Porous chemical mechanical polishing pads

ABSTRACT

Implementations disclosed herein generally relate to polishing articles and methods for manufacturing polishing articles used in polishing processes. More specifically, implementations disclosed herein relate to porous polishing pads produced by processes that yield improved polishing pad properties and performance, including tunable performance. Additive manufacturing processes, such as three-dimensional printing processes provides the ability to make porous polishing pads with unique properties and attributes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of co-pending U.S. patent applicationSer. No. 15/394,044, filed Dec. 29, 2016, which claims the benefit ofU.S. provisional patent application Ser. No. 62/280,537, filed Jan. 19,2016, the benefit of U.S. provisional patent application Ser. No.62/331,234, filed May 3, 2016, and the benefit of U.S. provisionalpatent application Ser. No. 62/380,015, filed Aug. 26, 2016. Theaforementioned related patent applications are incorporated herein byreference in their entirety.

BACKGROUND Field

Implementations disclosed herein generally relate to polishing articlesand methods for manufacturing polishing articles used in polishingprocesses. More specifically, implementations disclosed herein relate toporous polishing pads produced by processes that yield improvedpolishing pad properties and performance, including tunable performance.

Description of the Related Art

Chemical mechanical polishing (CMP) is a conventional process used inmany different industries to planarize surfaces of substrates. In thesemiconductor industry, uniformity of polishing and planarization hasbecome increasingly significant as device feature sizes continue todecrease. During a CMP process, a substrate, such as a silicon wafer, ismounted on a carrier head with the device surface placed against arotating polishing pad. The carrier head provides a controllable load onthe substrate to push the device surface against the polishing pad. Apolishing liquid, such as slurry with abrasive particles, is typicallysupplied to the surface of the moving polishing pad and polishing head.The polishing pad and polishing head apply mechanical energy to thesubstrate, while the pad also helps to control the transport of slurry,which interacts with the substrate during the polishing process.

A conventional polishing pad is typically made by molding, casting orsintering polymeric materials that include polyurethane materials. Inthe case of molding, polishing pads can be made one at a time, e.g., byinjection molding. In the case of casting, the liquid precursor is castand cured into a cake, which is subsequently sliced into individual padpieces. These pad pieces can then be machined to a final thickness. Padsurface features, including grooves, which aid in slurry transport, canbe machined into the polishing surface, or be formed as part of theinjection molding process.

Polishing pads made of harder materials often exhibit high removal ratesand have long useful pad life, but undesirably tend to form numerousscratches on the substrate being polished. Polishing pads made of softermaterials exhibit low scratching of substrates, but tend to exhibitlower removal rates and have shorter useful pad life.

In the case of porous polishing pads, open pore structures may beintroduced into the pad via methods including poromerics and closed porestructures may be introduced into the pad via methods including blendingwith microspheres, frothing, microcellular foaming, blending withwater-soluble spherical particles, and embedding with mineral oil. Thesemethods of manufacturing polishing pads are expensive and timeconsuming, and often yield non-uniform polishing results due to thedifficulties in the production and control of the dimensions of the padsurface features. Non-uniformity has become increasingly significant asthe dimensions of IC devices and feature sizes continue to shrink.

Accordingly, there remains a need in the art for polishing pads andmethods of manufacturing polishing pads that provide uniform removalrates, have extended pad life, and minimizes scratching of the polishedsubstrate.

SUMMARY

Implementations disclosed herein generally relate to polishing articlesand methods for manufacturing polishing articles used in polishingprocesses. More specifically, implementations disclosed herein relate toporous polishing pads produced by processes that yield improvedpolishing pad properties and performance. In one implementation, a resinprecursor composition is provided. The resin precursor compositioncomprises a first resin precursor component that comprises amultifunctional acrylate oligomer, a second resin precursor componentthat comprises a multifunctional acrylate monomer, a surfactant and aporosity-forming agent. In one configuration, the porosity-forming agentincludes water. The first precursor formulation has a first viscositythat enables the first precursor formulation to be dispensed to form aportion of the polishing article by use of an additive manufacturingprocess.

In another implementation, a composition for forming a porous polishingpad is provided. In another implementation, a porous polishing pad isprovided. The porous polishing pad is formed from a resin precursorcomposition comprising a first resin precursor component that comprisesa multifunctional acrylate oligomer, a second resin precursor componentthat comprises a multifunctional acrylate monomer, a surfactant and aporosity-forming agent. The first precursor formulation has a firstviscosity that enables the first precursor formulation to be dispensedto form a portion of the polishing article by use of an additivemanufacturing process.

In yet another implementation, a method of forming a porous polishingpad is provided. The method comprises depositing a plurality ofcomposite layers with a 3D printer to reach a target thickness.Depositing the plurality of composite layers comprises dispensing one ormore droplets of a curable resin precursor composition onto a support.The curable resin precursor composition comprises a first resinprecursor component that includes a multifunctional acrylate oligomer, asecond resin precursor component that comprises a multifunctionalacrylate monomer, a surfactant and a porosity-forming agent. The curableresin precursor composition has a first viscosity that enables thecurable resin precursor composition to be dispensed to form a portion ofthe polishing pad by use of an additive manufacturing process.Depositing further comprises exposing the dispensed first droplet of thecurable resin precursor composition to electromagnetic radiation for afirst time period partially curing the curable resin precursorcomposition, repeating the dispensing, and exposing to build a 3D-reliefon the support. The method further comprises solidifying the pluralityof composite layers to form a porous pad body.

In one implementation, the porosity-forming agent is vaporizable. In oneimplementation, the porosity-forming agent is selected from the group ofwater, water-soluble inert materials, water-containing hydrophilicpolymers, hydrophilic polymerizable monomers, and combinations thereof.

In one implementation, the porosity-forming agent contains ionicsurfactants, glycols, or mixtures thereof. The ionic surfactantsinclude, for example, ammonium-based salts. Exemplary salts includetetrabutylammonium tetrabutylborate, tetrafluoroborate,hexafluorophosphate, tetrabutylammonium benzoate, or combinationsthereof. Exemplary glycols include diethylene glycol and propyleneglycol. This non-reactive ionic surfactant/glycol mixture is dispersedinto photo-curable ink formulations. After curing, nano-sized andmicro-sized mixture drops are trapped in the cured materials. During CMPpolishing, mixture drops dissolve into the polishing slurry leavingporous features in the CMP surface. This benefits pad surfaceinteraction with slurry and slurry nanoparticle loading on pads; and inturn, enhances polishing removing rates and reduces the wafer-to-waferremoving rate deviation. Introduction of cationic materials can alsobond to the polymer chain by Norrish Type II reactions and furtherenhancing the positive zeta potential of the pad.

In yet another implementation, a method of forming a porous polishingpad is provided. The method comprises depositing a plurality ofcomposite layers with a 3D printer to reach a target thickness.Depositing the plurality of composite layers comprises dispensing one ormore droplets of a curable resin precursor composition onto a supportand dispensing one or more droplets of a porosity-forming compositiononto the support, wherein at least one component of the porosity-formingcomposition is removable to form the pores in the porous polishing pad.

In yet another implementation, a method of forming a porous polishingpad is provided. The method comprises depositing a plurality ofcomposite layers with a 3D printer to reach a target thickness andsolidifying the plurality of composite layers to form a porous pad body.Depositing the plurality of composite layers comprises dispensing one ormore droplets of a curable resin precursor composition onto a support.The curable resin precursor composition comprises a first resinprecursor component that comprises a multifunctional acrylate oligomer,a second resin precursor component that comprises a multifunctionalacrylate monomer, a surfactant and a porosity-forming agent. Depositingthe plurality of composite layers further comprises exposing the one ormore droplets of the curable resin precursor composition toelectromagnetic radiation to at least partially cure the curable resinprecursor composition and repeating the dispensing and exposing to builda 3D-relief on the support.

In yet another implementation, a resin precursor composition isprovided. The resin precursor composition comprises a first precursorformulation. The first precursor composition comprises a first resinprecursor component that comprises a multifunctional acrylate oligomer,a second resin precursor component that comprises a multifunctionalacrylate monomer, a surfactant and water. The first resin precursorformulation has a viscosity that enables the first precursor formulationto be dispensed to form a portion of a polishing article by use of anadditive manufacturing process.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description ofthe implementations, briefly summarized above, may be had by referenceto implementations, some of which are illustrated in the appendeddrawings. It is to be noted, however, that the appended drawingsillustrate only typical implementations of this disclosure and aretherefore not to be considered limiting of its scope, for the disclosuremay admit to other equally effective implementations.

FIG. 1 is a schematic sectional view of a polishing station having aporous polishing pad formed according to implementations describedherein;

FIG. 2A is a schematic isometric and cross-sectional view of a porouspolishing pad according to an implementation of the present disclosure;

FIG. 2B is a schematic partial top view of a porous polishing padaccording to an implementation of the present disclosure;

FIG. 2C is a schematic isometric and cross-sectional view of a porouspolishing pad according to an implementation of the present disclosure;

FIG. 2D is a schematic side cross-sectional view of a portion of aporous polishing pad according to an implementation of the presentdisclosure;

FIG. 2E is a schematic side cross-sectional view of a portion of aporous polishing pad according to an implementation of the presentdisclosure;

FIGS. 2F-2K are top views of polishing pad designs according toimplementations of the present disclosure.

FIG. 2L illustrates a plot of polished material removal rate versusfeature height of a polishing pad, according to an implementation of thepresent disclosure.

FIG. 2M illustrates a plot of surface area to volume ratio versusfeature height of a polishing pad, according to an implementation of thepresent disclosure.

FIG. 2N is a schematic cross-sectional view of a polishing pad accordingto an implementation of the present disclosure.

FIG. 2O is a schematic cross-sectional view of a polishing pad accordingto an implementation of the present disclosure.

FIG. 3A is a schematic view of a system for manufacturing porouspolishing pads, according to an implementation of the presentdisclosure;

FIG. 3B is a schematic view of a portion of the system illustrated inFIG. 3A, according to an implementation of the present disclosure;

FIG. 3C is a schematic view of a dispensed droplet disposed on a surfaceof a region of the porous polishing pad illustrated in FIG. 3B,according to an implementation of the present disclosure;

FIG. 4A is a schematic top view of a web or roll-to-roll type polishingpad, according to an implementation of the present disclosure;

FIG. 4B is a schematic side cross-sectional view of a portion of aporous polishing pad, according to an implementation of the presentdisclosure;

FIG. 5A is a top view of a pixel chart used to form an advancedpolishing pad that may contain pores, according to at least oneimplementation of the present disclosure;

FIG. 5B is a schematic side cross-sectional view of a portion of anadvanced polishing pad, according to an implementation of the presentdisclosure;

FIG. 5C is a schematic side cross-sectional view of a portion of anadvanced polishing pad, according to an implementation of the presentdisclosure;

FIG. 6A is a scanning electron microscope (SEM) image of oneimplementation of a porous pad structure formed according toimplementations described herein;

FIG. 6B is a scanning electron microscope (SEM) image of anotherimplementation of a porous pad structure formed according toimplementations described herein;

FIG. 7 is a schematic side cross-sectional view of a portion of a porouspolishing pad according to an implementation of the present disclosure;

FIG. 8 is a schematic side cross-sectional view of a porous polishingpad having a transparent region formed therein, according to animplementation of the present disclosure;

FIG. 9 is a schematic perspective sectional view of a porous polishingpad including a supporting foam layer, according to an implementation ofthe present disclosure;

FIGS. 10A-10O depict SEM images of various implementations of porouspads formed according to implementations described herein;

FIG. 11A-11B depict SEM images of surfaces of porous pads formedaccording to implementations described herein;

FIG. 12 depict SEM images of surfaces of porous pads formed according toimplementations described herein; and

FIG. 13 is a flow chart depicting a method of forming a porous padaccording to implementations described herein.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneimplementation may be beneficially incorporated in other implementationswithout further recitation.

DETAILED DESCRIPTION

Implementations disclosed herein generally relate to polishing articlesand methods for manufacturing polishing articles used in polishingprocesses. More specifically, implementations disclosed herein relate toporous polishing pads produced by processes that yield improvedpolishing pad properties and performance, including tunable performance.Additive manufacturing processes, such as three-dimensional printing(“3D printing”) processes provide the ability to make polishing padswith unique properties and attributes. Implementations of the presentdisclosure provide an advanced polishing pad that has discrete featuresand geometries, formed from at least two different materials that areformed from liquid polymer precursors, or resin precursor compositions,that contain “resin precursor components.” The resin precursorcomponents include, but are not restricted to functional polymers,functional oligomers, monomers, reactive diluents, flow additives,curing agents, photoinitiators, one or more porosity-forming agents,surfactants and cure synergists.

Material and microstructure variations over length scales of a deposited20-100 micron region are reproducible. This attribute may enable CMPprocess performance tuning on an unprecedented level. One technique for3D printing utilizes inkjet technology, which involves dispensing adroplet of a liquid resin precursor composition in a predeterminedpattern and curing or solidifying the dispensed precursor material intoa solid polymer by exposing the dispensed precursor material toelectromagnetic radiation, such as ultraviolet light. Inkjet technologyproduces microdroplets of precursor material by ejecting precursormaterials through a small nozzle (e.g., 10-50 micron diameter). Thiscreates high pressure and shear on the droplet. Additionally 3D printingtechniques involve printing material in a layer-by-layer form, wherethickness control of each deposited layer is critical.

Typically, complex shapes are created with 3D printing techniques, wherethe matrix material itself is solid. Implementations described herein,disclose a resin precursor composition for forming porous structures byincorporating one or more liquid porosity-forming agents in the resinprecursor composition, which is also referred to herein as the liquidpolymer precursor material. While, for simplicity reasons, thediscussion below primarily discloses the use of water as the“porosity-forming agent” in a resin precursor composition, this type ofporosity-forming agent is not intended to be limiting as to the scope ofthe disclosure provided herein since other non-miscible liquidcomponents (e.g., organic liquids) may be used in its place within theresin precursor composition. Porosity-forming agents that may be usedwith the implementations described herein include but are not limited towater, water-soluble inert materials, water-containing hydrophilicpolymers, hydrophilic polymerizable monomers, and combinations thereof.In some cases, it is also desirable for the porosity-forming agent to bevaporizable at temperatures below the decomposition temperature ofpolymer materials used to form the porous polishing pad. In someimplementations where the porosity-forming agent is soluble in water orother solvents, the porosity-forming agent may be removed by a rinsingprocess to form the porous pad structure.

In some implementations described herein, the resin precursorcomposition further comprises a low hydrophilic lyophilic balance(“HLB”) surfactant. In some implementations, since water, or otherporosity-forming agents, is immiscible in the liquid polymer precursorsfound in the resin precursor composition and the water's dispersion maybe aided by adding the low HLB surfactant, a uniform dispersion of waterdroplets can be formed within the resin precursor composition. The typeand amount of surfactant used determine the size of porosity-formingagent droplets in the resulting emulsion. The water-liquid polymerprecursor emulsion of the resin precursor composition is dispensedthrough the ink-jet printer and on exposure to energy (e.g., UV light),forms a solid polymer, which encloses porosity-forming agentmicro-droplets. The final solidified material may be dried at atemperature below the softening temperature of the solid polymer toeliminate the residual porosity-forming agent, leaving a porousmaterial. In one example, between about 5 wt. % to about 40 wt. % of aporosity-forming agent may be incorporated in the liquid polymerprecursor formulation as discussed further below. In another example,between about 5 wt. % to about 30 wt. % of water may be incorporated inthe liquid polymer precursor formulation as discussed further below.Suitable low HLB surfactants include, but are not limited to sorbitanstearate (HLB 4.7), polyglyceryl oleate (HLB 5.0), lecithin (HLB approx.4.0), sorbitan monooleate, glyceryl monooleate, and lanolin & lanolinalcohols.

In some implementations, the porosity-forming agent is depositedseparately from the resin precursor formulation. For example, the resinprecursor formulation is deposited from a first nozzle and theporosity-forming agent is deposited from a second nozzle. Deposition ofthe resin precursor formulation and the porosity-forming agent may befollowed by at least one of a curing process to form or partially formthe porous structure, a rinsing process to remove the porosity-formingagent, and an annealing process to form the final porous structure.

Implementations of the present disclosure further provide polishingarticles and methods of forming polishing articles that are porous andhave varying regions of zeta potential throughout the surface of thepolishing article. The varying regions of zeta potential of thepolishing article may be tuned based on the slurry composition systemsused and the materials to be polished. This varying zeta potential maybe tuned to transport active slurry to the interface between thepolishing article and substrate while removing polishing byproducts andcontaminants from the interface. For example, in some implementations,the polishing article has a more positive zeta potential near thepolishing surface of the polishing article (i.e. the interface betweenthe polishing article and the liquid interface) and a more negative zetapotential near the bottom of a groove of the polishing article. The morepositive zeta potential repels unwanted positively charged ions (e.g.,metal ions, dielectric material ions) from the liquid interface whilethe more negative zeta potential attracts the unwanted positive ionstoward the bottom of the groove where the collected ions can be removedfrom the polishing article. In polishing systems where the active slurrycontains abrasives having a negative zeta potential (e.g., nativesilica, such as fumed silica), the abrasives may be attracted to themore positive zeta potential near the polishing surface andcorrespondingly repelled by the negative potential near the bottom ofthe groove. In some implementations where the active slurry contains anabrasives having a positive zeta potential (e.g., alumina) the polishingsurface may be designed to have a more negative zeta potential relativeto other regions of the surface of the polishing article to attract theabrasive to the interface between the polishing article and the liquidinterface.

The following disclosure describes a polishing pad for chemicalmechanical polishing comprising a porous polymeric material, wherein thepolishing pad includes a porous structure. The following disclosure alsodescribes formulations and processes for forming porous polishing pads.

Certain details are set forth in the following description and in FIGS.1-13 to provide a thorough understanding of various implementations ofthe disclosure. Other details describing well-known structures andsystems often associated with additive manufacturing processes andpolishing article manufacturing are not set forth in the followingdisclosure to avoid unnecessarily obscuring the description of thevarious implementations. Many of the details, dimensions, angles andother features shown in the Figures are merely illustrative ofparticular implementations. Accordingly, other implementations can haveother details, components, dimensions, angles and features withoutdeparting from the spirit or scope of the present disclosure. Inaddition, further implementations of the disclosure can be practicedwithout several of the details described below.

It should be understood that although the polishing articles describedherein are polishing pads, the implementations describe herein are alsoapplicable to other polishing articles including, for example, buffingpads. Further, although the polishing articles described herein arediscussed in relation to a chemical mechanical polishing process, thepolishing articles and methods of manufacturing polishing articlesdescribed herein are also applicable to other polishing processesincluding polishing lenses and other processes including both abrasiveand non-abrasive slurry systems. In addition, the polishing articlesdescribed herein may be used in at least the following industries:aerospace, ceramics, hard disk drive (HDD), MEMS and Nano-Tech,metalworking, optics and electro-optics, and semiconductor, amongothers.

As will be discussed further below, the porous polishing pads describedherein may be formed using an additive manufacturing process, forexample, a 3D printing process. In one non-limiting example of a 3Dprinting process, a layer of the porous polishing pad starts with a thinpattern of droplets of a resin precursor composition that are dispensedon a surface and are then cured to form the polishing article inlayer-by-layer fashion. Since 3D printing processes can exercise localcontrol over the material composition, microstructure and surfacetexture, various (and previously inaccessible) geometries may beachieved with this method.

In another non-limiting example of a 3D printing process, a layer of theporous polishing pad starts with a thin pattern of droplets of a resinprecursor composition that are dispensed on a surface from a firstnozzle and a thin pattern of droplets of porosity-forming agent isdeposited on the surface from a second nozzle. The thin pattern of theresin precursor composition and the porosity-forming agent are thencured to form the polishing article in layer-by-layer fashion. Since 3Dprinting processes can exercise local control over the materialcomposition, microstructure and surface texture, various (and previouslyinaccessible) geometries may be achieved with this method.

In some implementations, the polishing pad includes a porous structureformed within the printed solidified material that contains open poresand/or closed pores. In one implementation, the polishing pad includes aporous structure formed within the printed solidified material thatsubstantially contains closed pores. In another implementation, thepolishing pad includes a porous structure within the printed solidifiedmaterial that contains both open pores and closed pores. In one example,the open pores are formed at the polishing surface of the formedpolishing pad and the closed pores are formed at a level beneath thesurface of the polishing pad. Yet, in another implementation, it may bedesirable to form a polishing pad that includes a porous structurewithin the printed solidified material that contains substantially allopen pores, which may form an interwoven network of pores. However, insome implementations, the void volume of the porous polishing padpredominantly includes closed cells (i.e., closed pores). Preferably, atleast about 75% or more, for example, about 80% or more, about 85% ormore, about 90% or more, about 95% or more, about 98% or more, about 99%or more, or 100%, of the void volume of the porous polishing padincludes closed pores. In general, closed pores, or closed cells,include hollow interior regions of material that are not interconnected,or are only interconnected to a few adjacent cells. In someimplementations, the closed pores are predominantly buried within theporous pad material until they are exposed and/or opened at the padsurface due to pad wear or a pad conditioning process.

The porous polishing pad can have a void volume fraction of about 1% ormore, e.g., about 4% or more, about 5% or more, about 10% or more, about12% or more, about 15% or more, about 20% or more, about 25% or more,about 30% or more, about 40% or more, or about 45% or more.Alternatively, or in addition, the porous polishing pad can have a voidvolume fraction of about 50% or less, e.g., about 45% or less, about 40%or less, about 30% or less, about 25% or less, about 20% or less, about15% or less, about 12% or less, about 10% or less, about 5% or less, orabout 4% or less. Thus, the porous polishing pad can have a void volumefraction bounded by any two of the endpoints recited for the voidvolume. For example, the porous polishing pad can have a void volumefraction of about 1% to about 50%, about 10% to about 40%, about 20% toabout 30%, about 1% to about 20%, about 2% to about 18%, about 4% toabout 5%, about 5% to about 15%, about 10% to about 20%, about 25% toabout 30%, or about 35% to about 40%.

The void volume fraction of the porous polishing pad can be measuredusing any suitable measurement method. For example, the void volumefraction of the porous polishing pad can be measured using a densitymeasurement, wherein the void volume fraction can be expressed by: voidvolume %=(1−δ_(foamed)/δ_(solid))×100%, wherein δ_(foamed) is thedensity of the porous polishing pad and δ_(solid) is the density of thepolymeric resin used to form the porous polishing pad. The terms “voidvolume,” “void volume fraction,” or “void volume percentage” as usedherein can be synonymous with porosity.

The porous polishing pad, more specifically the closed pores of theporous polishing pad, can have an average pore size of about 1 μm ormore, e.g., about 5 μm or more, about 10 μm or more, about 15 μm ormore, about 20 μm or more, about 25 μm or more, about 30 μm or more,about 35 μm or more, about 40 μm or more, about 45 μm or more, about 50μm or more, about 55 μm or more, about 60 μm or more, about 65 μm ormore, about 70 μm or more, about 75 μm or more, about 100 μm or more,about 125 μm or more, or about 150 μm or more. Alternatively, or inaddition, the porous polishing pad can have an average pore size ofabout 200 μm or less, e.g., about 190 μm or less, about 180 μm or less,about 175 μm or less, about 170 μm or less, about 160 μm or less, about150 μm or less, 140 μm or less, 130 μm or less, about 125 μm or less,120 μm or less, 110 μm or less, 100 μm or less, 90 μm or less, 80 μm orless, 70 μm or less, 60 μm or less, 50 μm or less, 40 μm or less, 30 μmor less, about 20 μm or less; 15 μm or less, 10 μm or less, or 5 μm orless. Thus, the porous polishing pad can have an average pore sizebounded by any two of the endpoints recited for the average pore size.For example, the porous polishing pad can have an average pore size ofabout 1 μm to about 200 μm, about 5 μm to about 200 μm, about 5 μm toabout 20 μm, about 5 μm to about 40 μm, about 5 μm to about 130 μm,about 25 μm to about 75 μm, about 50 μm to about 100 μm, about 75 μm toabout 125 μm, about 100 μm to about 150 μm, about 125 μm to about 175μm, or about 150 μm to about 200 μm.

As used herein, the average pore size refers to the average of thelargest diameter of a representative sample of individual pores in theporous polishing pad. The largest diameter is the same as the Feretdiameter. The largest diameter can be obtained from an image of asample, such as a scanning electron microscope image, either manually orby using image analysis software. Typically, the sample is obtained bysectioning a portion of a porous polishing pad.

The average pore size as used herein refers to the average pore sizewithin the bulk portion of the porous polishing pad, i.e., the portionof the porous polishing pad between, but not including, the surface(s)of the porous polishing pad. The surface can be the region of the padwithin about 5 mm, e.g., within about 4 mm, within about 3 mm, withinabout 2 mm, or within about 1 mm, of the pad surface as produced andbefore any finishing operations, such as skiving, dressing, or the like.

Porous Polishing Pad Designs

According to one or more implementations of the disclosure, it has beendiscovered that a porous polishing pad with improved polishing andmechanical properties can be produced by an additive manufacturingprocess. A porous polishing pad, which is formed by additivemanufacturing process, can be formed such that it has improved polishingperformance and properties over conventionally formed porous ornon-porous pads. The formed porous polishing pad generally includes apad body and discrete features produced over, upon, and within the padbody, that may be formed simultaneously from a plurality of differentmaterials and/or compositions of materials, thus enabling micron scalecontrol of the pad architecture and properties. The disclosure providedherein can thus be used to form a porous polishing pad that includesdesirable pad polishing properties over the complete polishing processrange. Typical polishing pad mechanical properties include both staticand dynamic properties of the polishing pad, which are affected by theindividual materials within the polishing pad and the compositeproperties of the complete polishing pad structure. The porous polishingpad may include regions that contain a plurality of discrete materialsand/or regions that contain gradients in material composition orporosity related properties (e.g., pore size, pore volume, etc.) in oneor more directions within the formed polishing pad. Examples of some ofthe mechanical properties that can be adjusted to form a porouspolishing pad that has desirable polishing performance over thepolishing process range include, but are not limited to storage modulusE′, loss modulus E″, hardness, yield strength, ultimate tensilestrength, elongation, thermal conductivity, zeta potential, massdensity, surface tension, Poison's ratio, fracture toughness, surfaceroughness (Ra) and other related properties. Examples of some of thedynamic properties that can be adjusted within an porous polishing padmay include, but are not limited to tan delta (tan δ), storage modulusratio (or E′30/E′90 ratio) and other related parameters, such as theenergy loss factor (KEL). The energy loss factor (KEL) is related to theelastic rebound and dampening effect of a pad material. KEL may bedefined by the following equation: KEL=tan δ*10¹²/[E′*(1+(tan δ)²)],where E′ is in Pascals. The KEL is typically measured using the methodof Dynamic Mechanical Analysis (DMA) at a temperature of 40° C., andfrequency of 1 or 1.6 hertz (Hz). Unless specified otherwise, thestorage modulus E′, the E′30/E′90 ratio and the percent recoverymeasurements provided herein were performed using a DMA testing processthat was performed at a frequency of about 1 hertz (Hz) and atemperature ramp rate of about 5° C./min. By controlling one or more ofthe pad properties, an improved the polishing process performance,improved polishing pad lifetime, improved polishing slurry retention andimproved polishing process repeatability can be achieved. Examples ofpad configurations that exhibit one or more these properties arediscussed further below in conjunction with one or more theimplementations discussed herein.

Polishing Pad Apparatus and Polishing Methods

The improved porous polishing pad designs disclosed herein can be usedto perform a polishing process in many different types of polishingapparatus. In one example, which is not intended to limit the scope ofthe disclosure provided herein, the porous polishing pad may be used ina polishing station that is used to polish semiconductor substrates.FIG. 1 is a schematic sectional view of a polishing station 100 having aporous polishing pad 106 formed according to the implementationsdescribed herein. The polishing station 100 may be positioned within alarger chemical mechanical polishing (CMP) system that contains multiplepolishing stations 100. The polishing station 100 includes a platen 102.The platen 102 may rotate about a central axis 104. The porous polishingpad 106 may be placed on the platen 102. While not intending to limitthe disclosure provided herein, typically, the porous polishing pad 106covers an upper surface 103 of the platen 102 which is at least one totwo times larger than the size of a substrate 110 (e.g., substratediameter) that is to be processed in the polishing station 100. In oneexample, the porous polishing pad 106 and platen 102 are between about 6inches (150 millimeters) and about 40 inches (1,016 millimeters) indiameter. The porous polishing pad 106 includes a polishing surface 112configured to contact and process one or more substrates 110. The platen102 supports the porous polishing pad 106 and rotates the porouspolishing pad 106 during polishing. A carrier head 108 may hold thesubstrate 110 being processed against the polishing surface 112 of theporous polishing pad 106. A polishing interface 130 is formed betweenthe polishing surface 112 and the substrate 110. The carrier head 108typically includes a flexible diaphragm 111 that is used to urge thesubstrate 110 against the porous polishing pad 106 and a carrier ring109 that is used to correct for an inherently non-uniform pressuredistribution found across the substrate's surface during the polishingprocess. The carrier head 108 may rotate about a central axis 114 and/ormove in a sweeping motion to generate relative motions between thesubstrate 110 and the porous polishing pad 106.

During polishing, a polishing fluid 116, such as an abrasive slurry ornon-abrasive slurry, may be supplied to the polishing surface 112 by adelivery arm 118. The polishing fluid 116 may contain abrasiveparticles, a pH adjuster and/or chemically active components to enablechemical mechanical polishing of the substrate. The slurry chemistry of116 is designed to polish substrate surfaces and/or features that mayinclude metals, metal oxides, and semimetal oxides. One will note thatthe surface topography of the porous polishing pad 106 is used tocontrol the transport of the polishing fluid 116 (e.g., slurry) whichinteracts with the substrate 110 during the polishing process. Forexample, the surface topology of the porous polishing pad 106 mayconsist of grooves, channels and other protuberances, which are formedby casting, molding, or machining, which may be disposed over, upon andwithin the porous polishing pad 106.

In some implementations, the polishing station 100 includes a padconditioning assembly 120 that includes a conditioning arm 122 andactuators 124 and 126. The actuators 124 and 126 are configured to causea pad conditioning disk 128 (e.g., diamond impregnated disk) to be urgedagainst and sweep across the polishing surface 112 at different timesduring the polishing process cycle to abrade and rejuvenate thepolishing surface 112 of the porous polishing pad 106. Duringprocessing, moving the porous polishing pad 106 and carrier head 108apply mechanical energy to the substrate 110, which in combination withthe chemicals and abrasive components in the polishing fluid 116, willcause the surface of the substrate to become planarized.

Porous Polishing Pad Configuration Examples

Examples of various structural configurations of porous polishing padsthat can be used in a polishing apparatus are discussed in conjunctionwith FIGS. 2A-2K. The porous polishing pads illustrated in FIGS. 2A-2Kmay be used, for example, in the polishing station 100 depicted inFIG. 1. Unless otherwise specified, the terms first polishing element(s)204 and the second polishing element(s) 206 broadly describe portions,regions and/or features within the polishing body of a porous polishingpad 200. The specific examples of different porous polishing padconfigurations, shown in FIGS. 2A-2K, are not intended to be limiting asto the scope of the disclosure provided herein, since other similarconfigurations may be formed by use of the one or more of the additivemanufacturing processes described herein.

The porous polishing pads may be formed by a layer-by-layer automatedsequential deposition of at least one resin precursor compositionfollowed by at least one curing step, wherein each layer may representat least one polymer composition, and/or regions of differentcompositions. The compositions may include functional polymers,functional oligomers, porosity-forming agent(s),emulsifiers/surfactants, photoinitiators inorganic particles, reactivediluents, and additional additives. The functional polymers may includemultifunctional acrylate precursor components. To form a plurality ofsolid polymeric layers, one or more curing steps may be used, such asexposure of one or more compositions to UV radiation and/or thermalenergy. In this fashion, an entire polishing pad may be formed from aplurality of polymeric layers by an additive manufacturing process. Athickness of the cured layer may be from about 0.1 micron to about 1 mm,such as 5 microns to about 100 microns, and such as 25 microns to about30 microns.

The porous polishing pads according to the present disclosure may havediffering porosity across a pad body 202, as reflected by at least onecompositional gradient from polishing element to polishing element.Porosity across the porous polishing pad 200 may be symmetric ornon-symmetric, uniform or non-uniform to achieve target polishing padproperties, which may include static mechanical properties, dynamicmechanical properties and wear properties. In one implementation, thepores form near the interface of each adjacent deposited layer. Thepatterns of either of the polishing elements 204, 206 across the padbody 202 may be radial, concentric, rectangular, spiral, fractal orrandom according to achieve target properties including porosity, acrossthe porous polishing pad. Advantageously, the 3D printing processenables specific placement of material compositions with desiredproperties in specific areas of the pad, or over larger areas of thepad, so the properties can be combined and represent a greater averageof properties or a “composite” of the properties.

FIG. 2A is a schematic perspective sectional view of a porous polishingpad 200 a according to one implementation of the present disclosure. Oneor more first polishing elements 204 a may formed in alternatingconcentric rings that are coupled to one or more second polishingelement(s) 206 a to form a pad body 202 that is circular. At least oneof the one or more first polishing elements 204 a and the one or moresecond polishing element(s) 206 a may be porous and formed according tothe implementations described herein. In one implementation, a height210 of the first polishing element(s) 204 a from the supporting surface203 is higher than a height 212 of the second polishing element(s) 206 aso that the upper surface(s) 208 of the first polishing element(s) 204 aprotrude above the second polishing element(s) 206 a. In oneimplementation, the first polishing element 204 is disposed over aportion 212A of the second polishing element(s) 206 a. Grooves 218 orchannels are formed between the first polishing element(s) 204 a, and atleast include a portion of the second polishing element(s) 206 a. Duringpolishing, the upper surface(s) 208 of the first polishing elements 204a form a polishing surface that contacts the substrate, while thegrooves 218 retain and channel the polishing fluid. In oneimplementation, the first polishing element(s) 204 a are thicker thanthe second polishing element(s) 206 a in a direction normal to a planeparallel to the polishing surface, or upper surface(s) 208, of the padbody 202 (i.e., Z-direction in FIG. 2A) so that the channels or grooves218 are formed on the top surface of the pad body 202.

In one implementation, a width 214 of the first polishing elements 204 amay be between about 250 microns and about 5 millimeters. The pitch 216between the hard first polishing element(s) 204 a may be between about0.5 millimeters and about 5 millimeters. Each first polishing element204 a may have a width within a range between about 250 microns andabout 2 millimeters. The width 214 and/or the pitch 216 may vary acrossa radius of the porous polishing pad 200 to define zones of variedhardness, porosity, or both hardness and porosity.

FIG. 2B is a schematic partial top view of a porous polishing pad 200 baccording to an implementation of the present disclosure. The porouspolishing pad 200 b is similar to the porous polishing pad 200 of FIG.2A except that the porous polishing pad 200 b includes interlockingfirst polishing elements 204 b and second polishing elements 206 b. Atleast one of the interlocking first polishing elements 204 b and thesecond polishing elements 206 b may be porous and formed according tothe implementations described herein. The interlocking first polishingelements 204 b and the second polishing elements 206 b form a pluralityof concentric rings. The interlocking first polishing elements 204 b mayinclude protruding vertical ridges 220 and the second polishing elements206 b may include vertical recesses 222 for receiving the verticalridges 220. Alternatively, the second polishing elements 206 b mayinclude protruding ridges while the interlocking first polishingelements 204 b include recesses. By having the second polishing elements206 b interlock with the interlocking first polishing elements 204 b,the porous polishing pad 200 b will be mechanically stronger in relationto applied shear forces, which may be generated during the CMP processand/or material handling. In one implementation, the first polishingelements and the second polishing elements may be interlocked to improvethe strength of the porous polishing pad and improve physical integrityof the porous polishing pads. The interlocking of the features may bedue to physical and/or chemical forces.

FIG. 2C is a schematic perspective sectional view of a porous polishingpad 200 c according to an implementation of the present disclosure. Theporous polishing pad 200 c includes a plurality of first polishingelements 204 c extending from a base material layer, such as the secondpolishing element 206 c. At least one of the one the plurality of firstpolishing elements 204 c and the second polishing element 206 c may beporous and formed according to the implementations described herein.Upper surface(s) 208 of the first polishing elements 204 c form apolishing surface for contacting the substrate during polishing. Thefirst polishing elements 204 c and the second polishing elements 206 chave different material and structural properties. For example, thefirst polishing elements 204 c may be formed from a porous material,while the second polishing elements 206 c may be formed from anon-porous material as described herein. The porous polishing pad 200 cmay be formed by 3D printing, similar to the porous polishing pad 200.

The first polishing elements 204 c may be substantially the same size,or may vary in size to create varied mechanical properties, such asporosity, across the porous polishing pad 200 c. The first polishingelements 204 c may be uniformly distributed across the porous polishingpad 200 c, or may be arranged in a non-uniform pattern to achieve targetproperties in the porous polishing pad 200 c.

In FIG. 2C, the first polishing elements 204 c are shown to be circularcolumns extending from the second polishing elements 206 c.Alternatively, the first polishing elements 204 c may be of any suitablecross-sectional shape, for example columns with toroidal, partialtoroidal (e.g., arc), oval, square, rectangular, triangular, polygonal,or other irregular section shapes, or combinations thereof. In oneimplementation, the first polishing elements 204 c may be of differentcross-sectional shapes to tune hardness, mechanical strength or otherdesirable properties of the porous polishing pad 200 c.

FIG. 2D is a schematic partial side cross-sectional view of a pad body202 of a porous polishing pad 200 d according to an implementation ofthe present disclosure. The porous polishing pad 200 d is similar to theporous polishing pad 200 a, 200 b or 200 c of FIGS. 2A-2C except thatthe porous polishing pad 200 d includes interlocking first polishingelements 204 d and second polishing elements 206 d. At least one of theone the plurality of interlocking first polishing elements 204 d and thesecond polishing element 206 d may be porous and formed according to theimplementations described herein. The interlocking first polishingelements 204 d and the second polishing elements 206 d may include aplurality of concentric rings and/or discrete elements that form part ofthe pad body 202, which are illustrated, for example, in FIG. 2A, 2B or2C. In one implementation, the interlocking first polishing elements 204d may include protruding sidewalls 224 while the second polishingelements 206 d may include regions 225 to receive the protrudingsidewalls 224 of the interlocking first polishing elements 204 d.Alternatively, the second polishing elements 206 d may includeprotruding sidewalls while the interlocking first polishing elements 204d include regions that are configured to receive the protrudingsidewalls. By interlocking the second polishing elements 206 c with theinterlocking first polishing elements 204 d, the porous polishing pad200 d may exhibit an increased tensile, compressive and/or shearstrength. Additionally, the interlocking sidewalls prevent the porouspolishing pad 200 d from being pulled apart.

In one implementation, the boundaries between the interlocking firstpolishing elements 204 d and second polishing elements 206 d include acohesive transition from at least one composition of material toanother, such as a transition or compositional gradient from a firstcomposition used to form the interlocking first polishing element 204 dand a second composition used to form the second polishing element 206d. The cohesiveness of the materials is a result of the additivemanufacturing process described herein, which enables micron scalecontrol and intimate mixing of the two or more chemical compositions ina layer-by-layer additively formed structure.

FIG. 2E is a schematic partial sectional view of a porous polishing pad200 e according to an implementation of the present disclosure. Theporous polishing pad 200 e is similar to the porous polishing pad 200 dof FIG. 2D except that the porous polishing pad 200 e includesdifferently configured interlocking features. The porous polishing pad200 e may include first polishing elements 204 e and second polishingelements 206 e having a plurality of concentric rings and/or discreteelements. At least one of the one the first polishing elements 204 e andthe second polishing elements 206 e may be porous and formed accordingto the implementations described herein. In one implementation, thefirst polishing elements 204 e may include horizontal ridges 226 whilethe second polishing elements 206 e may include horizontal recesses 227to receive the horizontal ridges 226 of the first polishing elements 204e. Alternatively, the second polishing elements 206 e may includehorizontal ridges while the first polishing elements 204 e includehorizontal recesses. In one implementation, vertical interlockingfeatures, such as the interlocking features of FIG. 2B and horizontalinterlocking features, such as the interlocking features of FIGS. 2D and2E, may be combined to form a porous polishing pad.

FIGS. 2F-2K are schematic plan views of various polishing pad designsaccording to implementations of the present disclosure. Each of FIGS.2F-2K include pixel charts having white regions (regions in whitepixels) that represent the first polishing elements 204 f-204 k,respectively, for contacting and polishing a substrate, and blackregions (regions in black pixels) that represent the second polishingelement(s) 206 f-206 k. As similarly discussed herein, the white regionsgenerally protrude over the black regions so that channels are formed inthe black regions between the white regions. In one example, the pixelsin a pixel chart are arranged in a rectangular array type pattern (e.g.,X and Y oriented array) that are used to define the position of thevarious materials within a layer, or a portion of layer, of an porouspolishing pad. In another example, the pixels in a pixel chart arearranged in a hexagonal close pack array type of pattern (e.g., onepixel surrounded by six nearest neighbors) that are used to define theposition of the various materials within a layer, or a portion of layerof a polishing pad. Polishing slurry may flow through and be retained inthe channels during polishing. The polishing pads shown in FIGS. 2F-2Kmay be formed by depositing a plurality of layers of materials using anadditive manufacturing process. Each of the plurality of layers mayinclude two or more materials to form the first polishing elements 204f-204 k and second polishing element(s) 206 f-206 k. In oneimplementation, the first polishing elements 204 f-204 k may be thickerthan the second polishing element(s) 206 f-206 k in a direction normalto a plane that is parallel to the plurality of layers of materials sothat grooves and/or channels are formed on a top surface of thepolishing pad.

The first polishing elements 204 a-204 k in the porous polishing pads200 a-200 k of FIGS. 2A-2K may be formed from an identical material oridentical compositions of materials. Alternatively, the materialcomposition and/or material properties of the first polishing elements204 a-204 k in the designs of FIG. 2A-2K may vary from polishing featureto polishing feature. Individualized material composition and/ormaterial properties allow tailoring of the polishing pads for specificneeds.

It has been found that the structural configuration of the firstpolishing elements 204 relative to the second polishing elements 206 canalso be used to control polishing process repeatability and improve thepolishing rate of a polishing process. One such structural configurationrelates to the relative physical layout of the first polishing elements204 to the second polishing elements 206 in a formed advanced polishingpad, and is known herein as the total exposed surface area to volumeratio (SAVR) of the first polishing elements 204 within a formedadvanced polishing pad. It is believed that by adjusting the totalexposed surface area to volume ratio by controlling the relativephysical layout of the first polishing elements 204 relative to thesecond polishing elements 206 and the mechanical properties (e.g.,thermal conductivity, hardness, loss modulus, polishing contact area,etc.) of the materials used to form the first polishing elements 204and/or the second polishing elements 206, the polishing processrepeatability and substrate polishing rate can, along with otherpolishing parameter, be greatly improved. In one example, the mechanicalproperties of the material(s) within the first polishing elements 204include a thermal diffusivity (m²/s) that is less than about 6.0×10⁻⁶,such as between about 1.0×10⁻⁷ and 6.0×10⁻⁶ m²/s.

FIG. 2N illustrates two first polishing elements 204 _(A1) and 204 _(A2)that are supported by a second polishing element 206, such that aportion of the each of the first polishing elements 204 _(A1) and 204_(A2) is embedded within a portion of the second polishing element 206.The second polishing element 206 has a base surface 2061, which issupported by components in a polishing tool (not shown). The embeddedregion of the first polishing element is generally described herein asbeing an unexposed portion 2041 and the portion of the first polishingelements that is not embedded within the second polishing element 206 isreferred to herein as the exposed portion 2040. Each of the firstpolishing elements 204 _(A1) and 204 _(A2) have a feature height 2021that extends from the surface 2060 of the second polishing element 206to the top surface 2011 of each first polishing element 204. The firstpolishing elements 204 _(A1) and 204 _(A2), which are formed within anarray of first polishing elements, have a spacing 2020 that may beconstant or vary within the X-Y plane depending on the configuration ofthe advanced polishing pad. In some implementations, as illustrated inFIGS. 2A and 2F-2K the spacing 2020 within the array may be oriented ina radial direction (e.g., X-Y plane) and an arc direction (e.g., X-Yplane), and may be constant or vary in one or more of these directions,as discussed above.

Structurally the first polishing elements 204 _(A1), 204 _(A2) each havean exposed surface that includes a portion of the sides 2010 that isabove the surface 2060 of the second polishing element 206 and a topsurface 2011, on which a substrate is placed during polishing. In oneexample, first polishing elements, which are configured similarly to thefirst polishing elements illustrated in FIG. 2A, have a total surfacearea that varies depending on the radial position of each of the firstpolishing elements (e.g., concentric rings of differing diameters).Whereas, in another example, for the first polishing elements that areconfigured similarly to the first polishing elements illustrated in FIG.2C, the total exposed surface area of each first polishing element maynot vary from one first polishing element to the next. In general, thetotal exposed surface area (TESA) of each first polishing element 204includes the substrate contact area (SCA), which is the area of the topsurface 2011, and the total exposed sidewall area of the first polishingelement, which is the sum of the areas of the exposed portions of eachof the sides 2010.

One will note that the total surface contact area, which is generallythe area that a substrate contacts as it is being polished, is the sumof all of the areas of the top surfaces 2011 of all of the firstpolishing elements 204 in an advanced polishing pad. However, thepercent contact area is the total contact area of the first polishingelements 204 divided by the total pad surface area of the polishing pad(e.g., πD²/4, where D is the outer diameter of the pad). The volume (V)of a first polishing element, is generally the total internal volume ofa first polishing element 204, such as, for example, the volume of acylinder for the first polishing elements 204 illustrated in FIG. 2C.However, the total exposed surface area to volume ratio (SAVR) for firstpolishing elements 204 (e.g., SAVR=TESA/V), which have a similarcross-sectional shape, such as have the same radial width (e.g., width214 in FIG. 2A) or feature size (e.g., length 208L in FIG. 2C), embeddeddepth within the second polishing element 206 and polishing elementheight, will generally have the same total exposed surface area tovolume ratio for each of the first polishing elements 204 in the arrayused to form the advanced polishing pad.

FIG. 2O illustrates two first polishing elements 204 _(B1) and 204 _(B2)that are each supported by separate second polishing elements 206, andhave differing feature heights 2021 _(B1), 2021 _(B2). During apolishing process, the friction created between the top surface of eachof the first polishing elements 204 _(B1) and 204 _(B2) and therespective substrates, generates a heat flux 2071 or a heat flux 2072that are conducted away from the top surface of each of the firstpolishing elements 204 _(B1) and 204 _(B2). In general, the heat fluxes2071, 2072 will be similar if the surface properties of the top surface2011 and polishing parameters used to polish the substrate remain thesame for each of these configurations. However, it has been found thatthe exposed surface area and volume of the first polishing elements 204_(B1) and 204 _(B2) has an effect on the polishing process results, duein part to a difference in temperature that is achieved in differentlyconfigured first polishing elements 204 _(B1) and 204 _(B2) duringnormal polishing. An increase in process temperature will generallycause degradation in the mechanical properties of the polymer containingmaterial(s) used to form each of the differently configured firstpolishing elements 204 _(B1) and 204 ₆₂. Moreover, one will note thathigher polishing temperatures generally increase the polishing rate ofthe polishing process, and variations in the polishing processconditions from one substrate to the next is generally undesirable formost polishing processes.

Referring to FIG. 2O, convective heat transfer created by the movementof the polishing slurry relative to the exposed surfaces of the firstpolishing elements 204 _(B1) and 204 _(B2) will remove at least aportion of the heat generated during the polishing process. Typically,the polishing slurry is at a temperature below the normal temperature ofthe top surface (e.g., contact surface) of the first polishing elements204 _(B1) and 204 _(B2) during polishing. Therefore, at least due to: 1)the difference in the exposed surface area, which affects the ability ofthe differently configured first polishing elements to exchange heatwith the slurry, 2) the difference in the insulating effect of thesecond polishing element 206 due to the difference in feature heights,and 3) the difference in mass (e.g., volume) of the first polishingelements, the polishing process results will be different for the firstpolishing element 204 _(B1) and the first polishing element 204 _(B2).

FIG. 2L illustrates the effect of feature height 2021 on the removalrate for a first polishing element during a standard polishing process.As illustrated in FIG. 2O, material removal rate will increase as thefeature height is reduced. FIG. 2M illustrates the effect of featureheight 2021 on the total exposed surface area to volume ratio. It isbelieved that the structural and thermal effects created by thedifference in the total exposed surface area to volume ratio of theformed first polishing elements leads to the difference in the polishingprocess results for each of the differently configured first polishingelements (e.g., different feature height 2021) illustrated in FIG. 2L.

One will note that due to the need to “pad condition” the polymercontaining polishing pads, the act of abrading the top surface 2011 ofthe first polishing elements will decrease the feature height 2021 overthe lifetime of the polishing pad. However, the variation in featureheight 2021 will cause the total exposed surface area to volume ratio,and thus cause the polishing process results, to vary as the advancedpad is abraded by the pad conditioning process. Therefore, it has beenfound that it is desirable to configure the first polishing elements 204in an advanced polishing pad, such that the total exposed surface areato volume ratio remains stable over the life of the polishing pad. Insome implementations, the total exposed surface area to volume ratio ofthe first polishing elements 204, which are partially embedded within asecond polishing element 206, are designed to have a total exposedsurface area to volume ratio of less than 20 per millimeter (mm⁻¹). Inanother example, the total exposed surface area to volume ratio of lessthan 15 mm⁻¹, such as less than 10 mm⁻¹, or even less than 8 mm⁻¹.

In some implementations, the first polishing elements 204 in an advancedpolishing pad are designed such that the total exposed surface area tovolume ratio is within a stable region, for example the SAVR is lessthan 20 mm⁻¹, and a porosity of the first polishing element 204 is addedand/or controlled so that the slurry retention at the top surface 2011is desirably maintained. It has been found that the addition of porousfeatures to the surface of the first polishing elements 204 can also beused to stabilize the temperature variation in the formed firstpolishing elements 204 from wafer to wafer, as similarly found byadjusting the total exposed surface area to volume ratio. In oneexample, the porosity of the formed first polishing element is formedsuch that the thermal diffusivity (m²/s) of the material is betweenabout 1.0×10⁻⁷ and 6.0×10⁻⁶ m²/s. The pores within the first polishingelement 204, can have an average pore size of about 50 nm or more, suchas about 1 μm to about 150 μm, and have a void volume fraction of about1% to about 50%.

Formulation and Material Examples

As discussed above, the materials used to form portions of the pad body202, such as the first polishing element 204 and second polishingelement 206 may each be formed from at least one ink jettablepre-polymer composition that may be a mixture of functional polymers,functional oligomers, surfactants, reactive diluents, porosity-formingagent(s) and curing agents to achieve the desired properties of theporous polishing pad. In general, during the additive manufacturingprocess, the pre-polymer inks or compositions may be processed afterbeing deposited by use of any number of means including exposure orcontact with radiation or thermal energy, with or without a curing agentor chemical initiator. In general, the deposited material can be exposedto electromagnetic radiation, which may include ultraviolet radiation(UV), gamma radiation, X-ray radiation, visible radiation, IR radiation,and microwave radiation and accelerated electrons and ion beams may beused to initiate polymerization reactions. For the purposes of thisdisclosure, we do not restrict the method of cure, or the use ofadditives to aid the polymerization, such as sensitizers, initiators,catalysts, and/or curing agents, such as through cure agents or oxygeninhibitors.

In one implementation, two or more polishing elements, such as the firstand second polishing elements 204 and 206, within a pad body 202 that isunitary, may be formed from the sequential deposition and postdeposition processing of at least one radiation curable resin precursorcomposition, wherein the compositions contain functional polymers,functional oligomers, monomers, porosity-forming agent(s) and/orreactive diluents that have unsaturated chemical moieties or groups,including but not restricted to: vinyl groups, acrylic groups,methacrylic groups, acrylamido groups, allyl groups, olefinic groups,and acetylene groups. During the porous polishing pad formation process,the unsaturated groups may undergo free radical polymerization whenexposed to radiation, such as UV radiation, in the presence of a curingagent, such as a free radical generating photoinitiator, such as anIrgacure® product manufactured by BASF of Ludwigshafen, Germany.

Two types of free radical photoinitiators may be used in one or more ofthe implementations of the disclosure provided herein. The first type ofphotoinitiator, also referred to herein as a bulk cure photoinitiator,is an initiator that cleaves upon exposure to UV radiation yielding afree radical immediately, which may initiate a polymerization. The firsttype of photoinitiator can be useful for both surface and through orbulk cure of the dispensed droplets. The first type of photoinitiatormay be selected from the group including, but not restricted to benzoinethers, benzyl ketals, acetyl phenones, alkyl phenones, and phosphineoxides. The second type of photoinitiator, also referred to herein as asurface cure photoinitiator, is a photoinitiator that is activated by UVradiation and forms free radicals by hydrogen abstraction from a secondcompound, which becomes the actual initiating free radical. This secondcompound is often called a co-initiator or polymerization synergist, andmay be an amine synergist.

Amine synergists are used to diminish oxygen inhibition, and therefore,the second type of photoinitiator may be useful for fast surface cure.The second type of photoinitiator may be selected from the groupincluding but not restricted to benzophenone compounds and thioxanthonecompounds. An amine synergist may be an amine with an active hydrogen,and in one implementation an amine synergist, such as an aminecontaining acrylate may be combined with a benzophenone photoinitiatorin a resin precursor composition formulation to: a) limit oxygeninhibition, b) fast cure a droplet or layer surface so as to fix thedimensions of the droplet or layer surface, and c), increase layerstability through the curing process. In some cases, to retard orprevent free radical quenching by diatomic oxygen, which slows orinhibits the free radical curing mechanism. One may choose a curingatmosphere or environment that is oxygen limited or free of oxygen, suchas an inert gas atmosphere, and chemical reagents that are dry, degassedand mostly free of oxygen.

It has been found that controlling the amount of the chemical initiatorin the printed formulation is a significant factor in controlling theproperties of a formed porous polishing pad, since the repeated exposureof underlying layers to the curing energy as the porous polishing pad isformed will affect the properties of these underlying layers. In otherwords, the repeated exposure of the deposited layers to some amount ofthe curing energy (e.g., UV light, heat, etc.) will affect the degree ofcure, or over curing the surface of that layer, within each of theformed layers. Therefore, in some implementations, it is desirable toensure that the surface cure kinetics are not faster than through-cure(bulk-cure), as the surface will cure first and block additional UVlight from reaching the material below the surface cured region; thuscausing the overall partially cured structure to be “under-cured.” Insome implementations, it is desirable to reduce the amount ofphotoinitiator to ensure proper chain extension and cross-linking. Ingeneral, higher molecular weight polymers will form with a slowercontrolled polymerization. It is believed that if the reaction productscontain too many radicals, reaction kinetics may proceed too quickly andmolecular weights will be low which will in turn reduce mechanicalproperties of the cured material.

In some implementations, the resin precursor composition includes apolymeric photoinitiator and/or an oligomer photoinitiator that has amoderate to high molecular weight that is selected so that it isrelatively immobile within bulk region of a dispensed droplet prior to,during and/or after performing a curing process on the droplet. Themoderate to high molecular weight type of photoinitiator is typicallyselected such that it will not, or at least minimally, migrate within apartially cured droplet. In one example, after UV or UV LED curing adroplet that has a moderate to high molecular weight type ofphotoinitiator, as compared with the traditional small molecular weightphotoinitiator, the polymeric and oligomeric photoinitiators will tendto be immobilized within the bulk region of cured material and notmigrate to or vaporize from the surface or interfacial region of thecured material, due to the photoinitiator's relatively high molecularweight. Since the moderate to high molecular weight type ofphotoinitiator is relatively immobile within the formed droplet, thecuring, composition and mechanical properties of the bulk region and thecuring, composition, mechanical properties and surface properties (e.g.,hydrophilicity) of the surface of the dispensed droplet will remainrelatively uniform and stable. In one example, the moderate to highmolecular weight type of photoinitiator may be a material that has amolecular weight that is greater than 600, such as greater than 1000. Inone example, the moderate to high molecular weight type ofphotoinitiator may be a material that is selected from the group of PLIndustrials PL-150 and IGM Resins Omnipol 1001. The immobile feature ofthe polymeric and oligomeric photoinitiators, in comparison to smallmolecular photoinitiators, will also enhance the health, safety, andenvironmental impact of the additive manufacturing process used to forman advanced polishing pad.

In some implementations, a moderate to high molecular weight type ofphotoinitiator is selected for use in a droplet formulation such that itwill not significantly alter the viscosity of the final formulation usedto form the droplet that is dispensed on the surface of the growingpolishing pad. Traditionally, lower molecular weight photoinitiatorundesirably alter the viscosity of the formulation used to form thedroplet. Therefore, by selecting a desirable moderate to high molecularweight type of photoinitiator the viscosity of the final dropletformulation can be adjusted or maintained at a level that can be easilydispensed by the deposition hardware, such as a print head, during anadditive manufacturing process (e.g., 3D printing process).

In some implementations, the first and second polishing elements 204 and206 may contain at least one oligomeric and/or polymeric segments,compounds, or materials selected from: polyamides, polycarbonates,polyesters, polyether ketones, polyethers, polyoxymethylenes, polyethersulfone, polyetherimides, polyimides, polyolefins, polysiloxanes,polysulfones, polyphenylenes, polyphenylene sulfides, polyurethanes,polystyrene, polyacrylonitriles, polyacrylates, polymethylmethacrylates,polyurethane acrylates, polyester acrylates, polyether acrylates, epoxyacrylates, polycarbonates, polyesters, melamines, polysulfones,polyvinyl materials, acrylonitrile butadiene styrene (ABS), halogenatedpolymers, block copolymers and copolymers thereof. Production andsynthesis of the compositions used to form the first polishing element204 and second polishing element 206 may be achieved using at least oneUV radiation curable functional and reactive oligomer with at least oneof the aforementioned polymeric and/or molecular segments, such as thatshown in chemical structure A:

The difunctional oligomer as represented in chemical structure A,bisphenol-A ethoxylate diacrylate, contains segments that may contributeto the low, medium, and high storage modulus E′ character of materialsfound in the first polishing element 204 and second polishing element206 in the pad body 202. For example, the aromatic groups may impartadded stiffness to the pad body 202 because of some local rigidityimparted by the phenyl rings. However, those skilled in the art willrecognize that by increasing the ether chain segment “n” will lower thestorage modulus E′ and thus produce a softer material with increasedflexibility. In one implementation, a rubber-like reactive oligomer,polybutadiene diacrylate, may be used to create a softer and moreelastic composition with some rubber-like elastic elongation as shown inchemical structure B:

Polybutadiene diacrylate includes pendant allylic functionality (shown),which may undergo a crosslinking reaction with other unreacted sites ofunsaturation. In some implementations, the residual double bonds in thepolybutadiene segment “m” are reacted to create crosslinks, which maylead to reversible elastomeric properties. In one implementation, anporous polishing pad containing compositional crosslinks may have apercent elongation from about 5% to about 40%, and a E′30:E′90 ratio ofabout 6 to about 15. Examples of some crosslinking chemistries includesulfur vulcanization and peroxide, such as tert-butyl perbenzoate,dicumyl peroxide, benzoyl peroxide, di-tert-butyl peroxide and the like.In one implementation, 3% benzoyl peroxide, by total formulation weight,is reacted with polybutadiene diacrylate to form crosslinks such thatthe crosslink density is at least about 2%.

Chemical structure C represents another type of reactive oligomer, apolyurethane acrylate, a material that may impart flexibility andelongation to the porous polishing pad. An acrylate that containsurethane groups may be an aliphatic or an aromatic polyurethaneacrylate, and the R or R′ groups shown in the structure may bealiphatic, aromatic, oligomeric, and may contain heteroatoms such asoxygen.

Reactive oligomers may contain at least one reactive site, such as anacrylic site, and may be monofunctional, difunctional, trifunctional,tetrafunctional, pentafunctional and/or hexafunctional and thereforeserve as foci for crosslinking. The oligomers may represent “soft” or alow storage modulus E′ materials, “medium soft” or medium storagemodulus E′ materials, or “hard” or high storage modulus E′ materials.The storage modulus E′ (e.g., slope, or Δy/Δx) increases from a soft andflexible and stretchable polyurethane acrylate to an acrylic acrylate,then to a polyester acrylate, and then to the hardest in the series, ahard and high storage modulus E″ epoxy acrylate. Functional oligomersmay be obtained from a variety of sources including Sartomer USA ofExton, Pa., Dymax Corporation of Torrington, Conn., USA, and AllnexCorporation of Alpharetta, Ga., USA.

In implementations of the disclosure, multifunctional acrylates,including di, tri, tetra, and higher functionality acrylates, may beused to create crosslinks within the material used to form, and/orbetween the materials found in, the first polishing element 204 andsecond polishing element 206, and thus adjust polishing pad propertiesincluding storage modulus E′, viscous dampening, rebound, compression,elasticity, elongation, and the glass transition temperature. It hasbeen found that by controlling the degree of crosslinking within thevarious materials used to form the first polishing element 204 andsecond polishing element 206 desirable pad properties can be formed.Moreover, by controlling the porosity characteristics (e.g., averagepore size, pore volume, etc.) of the material within one or more of thepolishing elements 204, 206 in the porous polishing pad, the padproperties can further tailored and or refined to achieve a furtherimproved polishing performance.

In some configurations, multifunctional acrylates may be advantageouslyused in lieu of rigid aromatics in a polishing pad formulation, becausethe low viscosity family of materials provides a greater variety ofmolecular architectures, such as linear, branched, and/or cyclic, aswell as a broader range of molecular weights, which in turn widens theformulation and process window. Some examples of multifunctionalacrylates are shown in chemical structures D(1,3,5-triacryloylhexahydro-1,3,5-triazine), and E (trimethylolpropanetriacrylate):

The type or crosslinking agent, chemical structure, or the mechanism(s)for forming the crosslinks are not restricted in the implementations ofthis disclosure. For example, an amine containing oligomer may undergo aMichael addition type reaction with acrylic moiety to form a covalentcrosslink, or an amine group may react with an epoxide group to create acovalent crosslink. In other implementations, the crosslinks may beformed by ionic or hydrogen bonding. The crosslinking agent may containlinear, branched, or cyclic molecular segments. The crosslinking agentmay further contain oligomeric and/or polymeric segments, and maycontain heteroatoms such as nitrogen and oxygen. Crosslinking chemicalcompounds that may be useful for polishing pad compositions areavailable from a variety of sources including Sigma-Aldrich of St.Louis, Mo., USA, Sartomer USA of Exton, Pa., Dymax Corporation ofTorrington, Conn., USA, and Allnex Corporation of Alpharetta, Ga., USA.

As mentioned herein, reactive diluents can be used as viscosity thinningsolvents that are mixed with high viscosity functional oligomers toachieve the appropriate viscosity formulation to allow the formulationto be deposited by an additive manufacturing process, followed bycopolymerization of the diluent(s) with the higher viscosity functionaloligomers when exposed to a curing energy. In one implementation, whenn˜4, the viscosity of bisphenol-A ethoxylate diacrylate may be about1350 centipoise (cP) at 25 degrees Celsius, a viscosity which may be toohigh to effect dispense of a such a material in a 3D printing process.Therefore, it may be desirable to mix bisphenol-A ethoxylate diacrylatewith a lower viscosity reactive diluents, such as low molecular weightacrylates, to lower the viscosity to about 1 cP to about 100 cP at 25°C., such as about 1 cP to about 20 cP at 25 degrees Celsius. The amountof reactive diluent used depends on the viscosity of the formulationcomponents and the diluent(s) themselves. For example, a reactiveoligomer of 1000 cP may involve at least 40% dilution by weight offormulation to achieve a target viscosity. Examples of reactive diluentsare shown in chemical structures F (isobornyl acrylate), G (decylacrylate), and H (glycidyl methacrylate):

The respective viscosities of F-G at 25 degrees Celsius are 9.5 cP, 2.5cP, and 2.7 cP, respectively. Reactive diluents may also bemultifunctional, and therefore may undergo crosslinking reactions orother chemical reactions that create polymer networks. In oneimplementation, glycidyl methacrylate (H), serves as a reactive diluent,and is mixed with a difunctional aliphatic urethane acrylates, so thatthe viscosity of the mixture is about 15 cP. The approximate dilutionfactor may be from about 2:1 to about 10:1, such as about 5:1. An amineacrylate may be added to this mixture, such as dimethylaminoethylmethacrylate, so that it is about 10% by weight of the formulation.Heating the mixture from about 25 degrees Celsius to about 75 degreesCelsius causes the reaction of the amine with the epoxide, and formationof the adduct of the acrylated amine and the acrylated epoxide. Asuitable free radical photoinitiator, such as Irgacure® 651, may be thenadded at 2% by weight of formulation, and the mixture may be dispensedby a suitable 3D printer so that a 20-micron thick layer is formed on asubstrate. In one example, the layer may then be cured by exposing thedroplet or layer for between about 0.1 μs to about 10 seconds, such asabout 15 seconds, to UV light from about 200 nm to about 400 nm using ascanning UV diode laser at an intensity of about 10 to about 50 mJ/cm²to create a thin polymer film. Reactive diluent chemical compounds thatmay be useful for 3D printed polishing pad compositions are availablefrom a variety of sources including Sigma-Aldrich of St. Louis, Mo.,USA, Sartomer USA of Exton, Pa., Dymax Corporation of Torrington, Conn.,USA, and Allnex Corporation of Alpharetta, Ga., USA.

Another method of radiation cure that may be useful in the production ofpolishing pads is cationic cure, initiated by UV or low energy electronbeam(s). Epoxy group containing materials may be cationically curable,wherein the ring opening polymerization of epoxy groups may be initiatedby cations such as protons and Lewis acids. The epoxy materials may bemonomers, oligomers or polymers, and may have aliphatic, aromatic,cycloaliphatic, arylaliphatic or heterocyclic structures; and caninclude epoxide groups as side groups or groups that form part of analicyclic or heterocyclic ring system.

UV-initiated cationic photopolymerization exhibits several advantagescompared to the free-radical photopolymerization including lowershrinkage, better clarity, better through cure via livingpolymerization, and the lack of oxygen inhibition. UV cationicpolymerization may polymerize classes of monomers, which cannot bepolymerized by free radical means, such as epoxides, vinyl ethers,propenyl ethers, siloxanes, oxetanes, cyclic acetals and formals, cyclicsulfides, lactones and lactams. These cationically polymerizablemonomers include both unsaturated monomers, such as glycidylmethacrylate (chemical structure H) that may also undergo free-radicalpolymerization through the carbon-carbon double bonds as describedherein. Photoinitiators that generate a photoacid when irradiated withUV light (˜225 to 300 nm) or electron beams include, but are not limitedto aryl onium salts, such as iodonium and sulfonium salts, such astriarylsulfonium hexafluorophosphate salts, which may be obtained fromBASF of Ludwigshafen, Germany (Irgacure® product).

In one implementation, the material(s) used to form the first polishingelement 204 and the second polishing element 206, and thus the pad body202, may be formed from the sequential deposition and cationic cure ofat least one radiation curable resin precursor composition, wherein thecompositions contain functional polymers, functional oligomers,monomers, porosity-forming agent(s) (e.g., water, organic liquids, orwater-soluble materials) and/or reactive diluents that have epoxygroups. Mixed free radical and cationic cure systems may be used to savecost and balance physical properties. In one implementation, the firstpolishing element 204 and the second polishing element 206, may beformed from the sequential deposition and cationic and free radical cureof at least one radiation curable resin precursor composition, whereinthe compositions contain functional polymers, functional oligomers,monomers, surfactants, porosity-forming agent(s), and reactive diluentsthat have acrylic groups and epoxy groups. In another implementation, totake advantage of the clarity and lack of light absorption inherent insome cationically cured systems, an observation window or CMP end-pointdetection window, which is discussed further below, may be formed from acomposition cured by the cationic method. In some implementations, someof the layers in the formed porous polishing pad may be formed by use ofa cationic curing method and some of the layers may be formed from afree radical curing method.

In one implementation, as is discussed further below, the 3D printedpolymer layers may contain inorganic and/or organic particles that areused to enhance one or more pad properties of selected material layersfound in the formed porous polishing pad 200. Because the 3D printingprocess involves layer-by-layer sequential deposition of at least onecomposition per layer, additional deposition of inorganic or organicparticles disposed upon or within a pad layer may also be desirable toobtain a certain pad property and/or to perform a certain function. Theinorganic or organic particles may be added during the porous polishingpad formation process to improve the ultimate tensile strength, improveyield strength, improve the stability of the storage modulus over atemperature range, improve heat transfer, adjust a surfaces zetapotential, and/or adjust a surface's surface energy. The particle type,chemical composition, or size, and the added particles may vary byapplication or desired effect that is to be achieved. The particles thatare integrated in a 3D printed polishing pad may also serve as foci forcrosslinking, which may lead to a higher storage modulus E′ depending ona percent by weight loading. In another example, a polymer compositioncontaining polar particles, such as ceria, may have a further affinityfor polar materials and liquids at the pad surface, such as CMPslurries.

Exemplary Formulations

The porous polishing pad described herein may be formed from at leastone resin precursor composition as described herein. The resin precursorcomposition may comprise at least one pre-polymer composition. Thepre-polymer composition may be an ink jettable pre-polymer composition.The resin precursor composition may comprise, consist essentially of, orconsist of at least one of: (1) one or more oligomer components, (2) oneor more monomer components, (3) porosity-forming agent(s), (4) one ormore emulsifiers/surfactants; (5) a photoinitiator component, (6)reactive diluents, (7) inorganic particles, organic particles or both,and (8) additional additives.

The resin precursor composition may comprise one or more oligomercomponents (1). Any suitable oligomer component capable of achievingdesired properties in the final porous polishing article may be used.The one or more oligomer components may comprise at least one of anacrylic oligomer, a urethane (meth)acrylate oligomer, a polyester based(meth)acrylate oligomer, a polyether based (meth)acrylate oligomer, asilicone based meth(acrylate), vinyl(meth)acrylates, an epoxy(meth)acrylate oligomer or any of the other oligomer componentsdescribed herein. The oligomer component may be of low viscosity, lowvolatility, high reactivity, and low glass transition temperature. Theoligomer component may be a multifunctional component. The functionalityof the oligomer component may be 3 or less. The functionality of theoligomer component may be 2 or less.

Examples of suitable acrylic oligomers include, but are not limited to,those under the designations of CN820, CN152, and CN146, etc. fromSartomer®. Examples of suitable urethane (meth)acrylates include, butare not limited to, aliphatic and aromatic urethane (meth)acrylatesunder the designations of CN929, CN966, CN978, CN981, CN991, CN992,CN994, CN997, CN1963, CN9006, CN9007, etc. from Sartomer® and those fromCytek® Surface Specialty under the designations of Ebecryl 8402, Ebecryl1290.

Examples of suitable polyester or polyether based (meth)acrylateoligomers include, but are not limited to, those under the designationsof CN292, CN293, CN294E, CN299, CN704, CN2200, CN2203, CN2207, CN2261,CN2261LV, CN2262, CN2264, CN2267, CN2270, CN2271E, CN2273, CN2279,CN2282, CN2283, CN2303, CN3200 etc. from Sartomer® USA, LLC. Examples ofsuitable epoxy (meth)acrylates oligomer include, but are not limited to,those under the designations of Ebecryl 3701, Ebecryl 3708, Ebecryl3200, Ebecryl 3600, etc. from Cytek® Surface Specialty, and CN151 fromSartomer®.

The one or more oligomer components may comprise at least 5 wt. %, 10wt. %, 15 wt. %, 20 wt. %, 25 wt. %, 30 wt. %, 35 wt. %, 40 wt. %, 45wt. %, 50 wt. %, or 55 wt. % based on the total weight of the resinprecursor composition. The one or more oligomer components may compriseup to 10 wt. %, 15 wt. %, 20 wt. %, 25 wt. %, 30 wt. %, 35 wt. %, 40 wt.%, 45 wt. %, 50 wt. %, 55 wt. %, or 60 wt. % based on the total weightof the resin precursor composition. The amount of the oligomer componentin the resin precursor composition may be from about 5 wt. % to about 60wt. % based on the total weight of the resin precursor composition(e.g., from about 10 wt. % to about 60 wt. %, from about 20 wt. % toabout 50 wt. %; from about 40 wt. % to about 50 wt. %; or from about 10wt. % to about 30 wt. %).

The resin precursor composition may further comprise one or more monomercomponents (2). The monomer component typically offers good solvency tothe oligomer component in ink formulations, which dilutes the ink to alow viscosity. The monomer component may also have a low glasstransition temperature, which contributes to the flexibility of inkafter curing. The monomer component may be a multifunctional component.The functionality of the monomer component may be 3 or less. Thefunctionality of the monomer component may be 2 or less. In oneimplementation, the monomer component comprises both mono-functional anddi-functional monomers.

Examples of suitable mono-functional monomers include, but are notlimited to, tetrahydrofurfuryl acrylate (e.g. SR285 from Sartomer®),tetrahydrofurfuryl methacrylate, vinyl caprolactam, isobornyl acrylate,isobornyl methacrylate, 2-phenoxyethyl acrylate, 2-phenoxyethylmethacrylate, 2-(2-ethoxyethoxy)ethyl acrylate, isooctyl acrylate,isodecyl acrylate, isodecyl methacrylate, lauryl acrylate, laurylmethacrylate, stearyl acrylate, stearyl methacrylate, cyclictrimethylolpropane formal acrylate, 2-[[(Butylamino) carbonyl]oxy]ethylacrylate (e.g. Genomer 1122 from RAHN USA Corporation),3,3,5-trimethylcyclohexane acrylate, and mono-functional methoxylatedPEG (350) acrylate, etc.

Examples of suitable di-functional monomers include, but not are limitedto, diacrylates or dimethacrylates of diols and polyether diols, such aspropoxylated neopentyl glycol diacrylate, 1,6-hexanediol diacrylate,1,6-hexanediol dimethacrylate, 1,3-butylene glycol diacrylate,1,3-butylene glycol dimethacrylate 1,4-butanediol diacrylate,1,4-butanediol dimethacrylate, alkoxylated aliphatic diacrylate (e.g.,SR9209A from Sartomer®), diethylene glycol diacrylate, diethylene glycoldimethacrylate, dipropylene glycol diacrylate, tripropylene glycoldiacrylate, triethylene glycol dimethacrylate, and alkoxylatedhexanediol diacrylates, e.g. SR562, SR563, SR564 from Sartomer®.

The one or more monomer components may comprise at least 10 wt. %, 15wt. %, 20 wt. %, 25 wt. %, 30 wt. %, 35 wt. %, 40 wt. %, 45 wt. %, 50wt. %, or 55 wt. % based on the total weight of the resin precursorcomposition. The one or more monomer components may comprise up to 15wt. %, 20 wt. %, 25 wt. %, 30 wt. %, 35 wt. %, 40 wt. %, 45 wt. %, 50wt. %, 55 wt. %, or 60 wt. % based on the total weight of the resinprecursor composition. The amount of the monomer component in the resinprecursor composition may be from about 10 wt. % to about 60 wt. %relative to the total weight of the resin precursor composition (e.g.,from about 30 wt. % to about 60 wt. %; from about 20 wt. % to about 50wt. %; from about 40 wt. % to about 50 wt. %; or from about 10 wt. % toabout 30 wt. %).

In some implementations, it is desirable to control the properties ofone or more of the polishing elements 204, 206 in the porous polishingpad by controlling the relative amounts of oligomers to monomers, oralso referred to herein as controlling the oligomer-monomer ratio, in aresin precursor composition to control the amount of cross-linkingwithin the cured material formed by the resin precursor composition. Bycontrolling the oligomer-monomer ratio in a resin precursor composition,the properties (e.g., mechanical, dynamic, polishing performance, etc.)of the formed material can be further controlled. In someconfigurations, monomers have a molecular weight of less than 600. Insome configurations, oligomers have a molecular weight of 600 or more.In some configurations, the oligomer-monomer ratio is defined as aweight ratio of the oligomer component to the monomer component, and istypically selected to achieve the desired strength and modulus. In someimplementations, the oligomer-monomer ratio is from about 3:1 to about1:19 (e.g., 2:1 to 1:2; 1:1 to 1:3; 3:1 to 1:1). In some implementationsthe oligomer-monomer ratio is from about 3:1 to about 1:3 (e.g., 2:1 to1:2; 1:1 to 1:3; 3:1 to 1:1). In one example, an oligomer-monomer ratioof 1:1 can be used to achieve desirable toughness properties such aselongation and storage modulus E′ while maintaining printability.

The resin precursor composition further comprises a porosity-formingagent (3). A porosity-forming agent may comprise at least 5 wt. %, 10wt. %, 15 wt. %, 20 wt. %, 25 wt. %, 30 wt. %, 35 wt. %, 40 wt. %, 45wt. %, 50 wt. %, or 55 wt. % of the total weight of the resin precursorcomposition. A porosity-forming agent may comprise up to 10 wt. %, 15wt. %, 20 wt. %, 25 wt. %, 30 wt. %, 35 wt. %, 40 wt. %, 45 wt. %, 50wt. %, 55 wt. %, or 60 wt. % of the total weight of the resin precursorcomposition. The amount of porosity-forming agent in the resin precursorcomposition may be from about 10 wt. % to about 40 wt. % relative to thetotal weight of the resin precursor composition (e.g., from about 20 wt.% to about 40 wt. %; from about 30 wt. % to about 40 wt. %; from about20 wt. % to about 30 wt. %; or from about 10 wt. % to about 40 wt. %).The amount of porosity-forming agent in the resin precursor compositionmay be from about 5 wt. % to about 30 wt. % relative to the total weightof the resin precursor composition (e.g., from about 5 wt. % to about 25wt. %; from about 10 wt. % to about 25 wt. %; from about 10 wt. % toabout 20 wt. %; or from about 10 wt. % to about 30 wt. %).

In one implementation, the porosity-forming agent (3) is selected fromwater, water-soluble polymers, water-soluble inert materials,water-containing hydrophilic polymers, hydrophilic polymerizablemonomers, ionic surfactants and combinations thereof. In oneimplementation, the porosity-forming agent is vaporizable, soluble inwater or soluble in another solvent.

In one implementation, the porosity-forming agent is water. Examples ofthe water include pure water or ultrapure water such as ion-exchangedwater, ultrafiltration water, reverse osmotic water, and distilledwater. In another implementation, the porosity-forming agent is anorganic liquid. Examples of an organic liquid include ethylene glycol.

In another implementation, the porosity-forming agent is a water-solubleinert material. The water-soluble inert material is added during theadditive manufacturing process and then removed to generate pores. Thewater-soluble inert material may be removed via a rinsing process. Insome implementations, the water-soluble inert material is inert to UVradiation used during the curing process. In some implementations, thewater-soluble inert material lowers the viscosity of the printablecomposition. In some implementations, as the deposited material iscured, the water-soluble inert material phase separates from theoligomers and monomers present.

Examples of suitable water-soluble inert materials include, but not arelimited to, glycols (e.g., polyethylene glycols), glycol-ethers, andamines. In one implementation, the water-soluble inert material isselected from the group comprising ethylene glycol, butanediol, dimerdiol, propylene glycol-(1,2) and propylene glycol-(1,3),octane-1,8-diol, neopentyl glycol, cyclohexane dimethanol(1,4-bis-hydroxymethylcyclohexane), 2-methyl-1,3-propane diol,glycerine, trimethylolpropane, hexanediol-(1,6), hexanetriol-(1,2,6)butane triol-(1,2,4), trimethylolethane, pentaerythritol, quinitol,mannitol and sorbitol, methylglycoside, also diethylene glycol,triethylene glycol, tetraethylene glycol, polyethylene glycols,dibutylene glycol, polybutylene glycols, ethylene glycol, ethyleneglycol monobutyl ether (EGMBE), diethylene glycol monoethyl ether,ethanolamine, diethanolamine (DEA), triethanolamine (TEA) andcombinations thereof.

In another implementation, the porosity-forming agent is awater-containing hydrophilic polymer. Examples of suitablewater-containing hydrophilic polymers include, but are not limited tovinyl polymers such as polyvinyl alcohol, polyvinylpyrrolidone (PVP) andpolyvinyl methyl ether.

In another implementation, the porosity-forming agent is hydrophilicpolymerizable monomer in water. Examples of suitable hydrophilicpolymerizable monomers in water include, but are not limited to,triethanolamine (TEA) surfactant, polyoxyethylene alkyl phenyl etherammonium sulfates, polyoxyethylene alkyl phenyl ethers, anionicphosphate esters, and combinations thereof. In one implementations, thewater-containing hydrophilic polymers are selected from Hitenol™(polyoxyethylene alkyl phenyl ether ammonium sulfate) and Noigen™(polyoxyethylene alkyl phenyl ether) surfactants commercially availablefrom Dai-Ichi Kogyo Seiyaku Co., Ltd. of Japan; and the Maxemul™(anionic phosphate ester) surfactants commercially available fromUniqema of The Netherlands. Suitable grades of some of the materialslisted above may include Hitenol BC-10™, Hitenol BC-20™, Hitenol BC-30™,Noigen RN-10™, Noigen RN-20™, Noigen RN-30™, Noigen RN-40™, and Maxemul6106™, which has both phosphonate ester and ethoxy hydrophilicity, anominal C₁₈ alkyl chain with an acrylate reactive group, and 6112™.

In another implementation, the porosity-forming agent contains ionicsurfactants, glycols, or mixtures thereof. The ionic surfactantsinclude, for example, ammonium-based salts. Exemplary ammonium-basedsalts include tetrabutylammonium tetrabutylborate, tetrafluoroborate,hexafluorophosphate, tetrabutylammonium benzoate, or combinationsthereof. Exemplary glycols include diethylene glycol and propyleneglycol. This non-reactive ionic surfactant/glycol mixture is dispersedinto photo-curable ink formulations. After curing, nano-sized andmicro-sized mixture drops are trapped in the cured materials. During CMPpolishing, mixture drops dissolve into the polishing slurry leavingporous features in the CMP surface. This benefits pad surfaceinteraction with slurry and slurry nanoparticle loading on pads; and inturn, enhances polishing removing rates and reduces the wafer-to-waferremoving rate deviation.

Introduction of cationic materials can also bond to the polymer chain byNorrish Type II reactions further enhancing the positive zeta potentialof the pad. These cationic materials contain active hydrogen and mayparticipate in the Norrish Type II reactions thus incorporating into thepolymer matrix. Not to be bound by theory but it is believed thataddition of higher concentrations (>10%) of acrylic group containingamino materials may increase positive zeta potential. Under suchconditions, the formulation becomes thermally unstable and getscross-linked. In order to overcome this issue, just cationic species areadded. These compounds are also miscible very well in the formulation.In some instances with polar components, during the curing thesematerials phase separate out to form islands that can be removed bytreating with water, as they are soluble in water. This will createpores. Exemplary structures of the cationic materials are as follows:

In one implementation, the porosity-forming agent is removed by at leastone of dissolution from the printed-pad during the polishing process;the porosity-forming agent is sublimated from the printed-pad throughannealing post print, and/or evaporated post-printing to createpores/voids within the pad.

The resin precursor composition further comprises one or moreemulsifiers (4). The one or more emulsifiers are selected from ananionic surfactant, a cationic surfactant, a nonionic surfactant, anamphoteric or a combination thereof. As used herein, “emulsifier” refersto any compound or substance that enables the formation of an emulsion.The emulsifier may be selected from any surface-active compound orpolymer capable of stabilizing emulsions, providing the emulsifiercontains at least one anionic, cationic, amphoteric or nonionicsurfactant and is used in sufficient quantities to provide the resinprecursor composition with a porosity-forming agent-in-liquid polymeremulsion. Typically, such surface-active compounds or polymer stabilizeemulsions by preventing coalescence of the dispersed amounts ofporosity-forming agent within the emulsion. The surface-active compoundsuseful as emulsifiers in the present resin precursor composition areanionic, cationic, amphoteric or nonionic surfactant or combination ofsurfactants. Mixtures of surfactants of different types and/or differentsurfactants of the same type can be used.

In one implementation, the emulsifier comprises a surfactant with an HLBranging from 3 to 20. In one implementation, the surfactant has an HLBof at least 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or19. In one implementation, the surfactant has an HLB of up to 4, 5, 6,7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20. Thus, thesurfactant can have an HLB bounded by any two of the aforementionedendpoints recited for the HLB. In one implementation, the emulsifiercomprises a surfactant having an HLB value ranging from 4 to about 14.In one implementation, the emulsifier comprises a surfactant having anHLB of 10 or less. In one implementation, the emulsifier comprises a lowHLB surfactant having an HLB value ranging from 3 to about 6.

In one implementation, the emulsifier is a nonionic surfactant. Somesuitable nonionic surfactants that can be used include polyoxyethylenealkyl ethers, polyoxyethylene alkyl phenyl ethers, alkylglucosides,polyoxyethylene fatty acid esters, sorbitan fatty acid esters, andpolyoxyethylene sorbitan fatty acid esters. Examples of suitablenonionic surfactants include, but are not limited to, octylphenolethyoxylate based surfactants (available from The Dow Chemical Companyas TRITON™ X-45, TRITON™ X-100, TRITON™ X-102, TRITON™ X-114, TRITON™X-305, TRITON™ X-405); benzyl-polyethylene glycol tert-octylphenyl ether(available from The Dow Chemical Company as TRITON™ CF-10); saturated,predominantly unbranched C₁₃C₁₅ oxo alcohol conforming to the followingstructure formula: RO(CH₂CH₂O)_(x)H, wherein R is C₁₃C₁₅ oxo alcohol andx is 3, 4, 5, 7, 8, 10, 11 or 30 (available from BASF as Lutensol® AO 3,Lutensol® AO 4, Lutensol® AO 5, Lutensol® AO 7, Lutensol® AO 79,Lutensol® AO 8, Lutensol® AO 89, Lutensol® AO 109, Lutensol® AO 11,Lutensol® AO 30, Lutensol® AO 3109); alkylpolyethylene glycol ethersmade from a linear, saturated C₁₆C₁₈ fatty alcohol, conforming to thefollowing structure formula: RO(CH₂CH₂O)_(x)H, wherein R is C₁₆C₁₈ fattyalcohol and x is 11, 13, 18, 25, 50, or 80 (available from BASF asLutensol® AT 11, Lutensol® AT 13, Lutensol® AT 18, Lutensol® AT 18Solution, Lutensol® AT 25 E, Lutensol® AT 25 Powder, Lutensol® AT 25Flakes, Lutensol® AT 50 E, Lutensol® AT 50 Powder, Lutensol® AT 50Flakes, Lutensol® AT 80 E, Lutensol® AT 80 Powder, Lutensol® AT 80Flakes); alkyl polyethylene glycol ethers based on C₁₀-Guebet alcoholand ethylene oxides (available from BASF as Lutensol® XP 30, Lutensol®XP 40, Lutensol® XP 50, Lutensol® XP 60, Lutensol® XP 69, Lutensol® XP70, Lutensol® XP 79, Lutensol® XP 80, Lutensol® XP 89, Lutensol® XP 90,Lutensol® XP 99, Lutensol® XP 100, Lutensol® XP 140); alkyl polyethyleneglycol ethers based on C₁₀-Guebet alcohol and alkylene oxides (availablefrom BASF as Lutensol® XL 40, Lutensol® XL 50, Lutensol® XL 60,Lutensol® XL 70, Lutensol® XL 79, Lutensol® XL 80, Lutensol® XL 89,Lutensol® XL 90, Lutensol® XL 99, Lutensol® XL 100, Lutensol® XL 140);polyoxyethylene alkylphenyl ether based surfactants (available fromMontello, Inc. as NOIGEN RN-10™, NOIGEN RN-20™, NOIGEN RN-30™, NOIGENRN-40™, NOIGEN RN-5065™); reactive surfactants with one reactive group(available from Ethox Chemicals, LLC as E-Sperse® RS-1616); reactivesurfactants with two reactive groups (available from Ethox Chemicals,LLC as E-Sperse® RS-1617); polyoxyethylene alkyl ether (available fromKao Corporation as EMULGEN 1118S-70, HLB value: 16.4); alkoxylatedsurfactants (available from Air Products and Chemical, Inc. as Nonidet™RK-18, Nonidet™ SF-3, Nonidet™ SF-5); alkoxylated surfactants (availablefrom Air Products and Chemical, Inc. as Nonidet™ RK-18, Nonidet™ SF-3,Nonidet™ SF-5); ethoxylated alcohol surfactants (available from AirProducts and Chemical, Inc. as Tomadol™ 1-3, Tomadol™ 1-5, Tomadol™ 1-7,Tomadol™ 1-9, Tomadol™ 23-1, Tomadol™ 3-3, Tomadol™ 23-5, Tomadol™23-6.5, Tomadol™ 400, Tomadol™ 600, Tomadol™ 900, Tomadol™ 1200);polyoxyethylene vegetable-based fatty ethers derived from lauryl, cetyl,stearyl and oleyl alcohols (available from Croda International Plc asBrij™ C10, Brij™ 010, Brij™ L23, Brij™ 58, Brij™ 93).

In one implementation, the emulsifier is an anionic surfactant. Somesuitable anionic surfactants, which can be used include (i) sulfonicacids and their salts, including alkyl, alkylaryl, alkylnapthalene, andalkyldiphenylether sulfonic acids, and their salts, having at least 6carbon atoms in the alkyl substituent, such as dodecylbenzensulfonicacid, and its sodium salt or its amine salt; (ii) alkyl sulfates havingat least 6 carbon atoms in the alkyl substituent, such as sodium laurylsulfate; (iii) the sulfate esters of polyoxyethylene monoalkyl ethers;(iv) long chain carboxylic acid surfactants and their salts, such aslauric acid, steric acid, oleic acid, and their alkali metal and aminesalts.

Examples of suitable anionic surfactants include, but are not limitedto, sodium dodecylsulfate, Poly(ethylene glycol) 4-nonylphenyl3-sulfopropyl ether potassium salt, surfactants having both phosphonateester and ethoxy hydrophilicity, a nominal C₁₈ alkyl chain with anacrylate reactive group (available from Croda International Plc asMAXEMUL™ 6106); reactive surfactants based on a styrenated phenolhydrophobe with one equivalent of allyl glycidyl ether, then ethoxylatedwith 16 moles of EO, sulfated, and neutralized (available from EthoxChemicals, LLC as E-Sperse® RS-1596); reactive surfactants based on thea styrenated phenol hydrophobe with two equivalents of allyl glycidylether, then ethoxylated with 15 moles of EO, sulfated, and neutralized(available from Ethox Chemicals, LLC as E-Sperse® RS-1618); E-Sperse®RS-1684, E-Sperse® RS-1685 (available from Ethox Chemicals, LLC);alternative anionic surfactants suitable for use with variousimplementations of the present disclosure include polyoxyethylenealkylphenyl ether ammonium sulfates (available from Montello, Inc. asHITENOL BC-10™, HITENOL BC-1025™, HITENOL BC-20™, HITENOL BC-2020™,HITENOL BC-30™); polyoxyethylene styrenated phenyl ether ammoniumsulfates (available from Montello, Inc. as HITENOL AR-10™, HITENOLAR-1025™, HITENOL AR-20™, HITENOL AR-2020™, HITENOL BC-30™); sodiumpolyoxyethylene alkylether sulfuric esters (available from Montello,Inc. as HITENOL KH-05™, HITENOL KH-10™, HITENOL KH-1025™, HITENOLBC-2020™, HITENOL BC-30™; polyoxyethylene nonylphenyl ether phosphates(available from SOLVAY as Rhodafac® RE 610, Rhodafac® RE 610/LC,Rhodafac® RE 610-E); alkyl phosphate esters (available from SOLVAY asRhodafac® RA 600, Rhodafac® RA 600-E); alkylphenol ethoxylate basedphosphate esters (available from SOLVAY as Rhodafac® RM 710, Rhodafac®RP 710); alkyldiphenyloxide disulfonate based surfactants (availablefrom The Dow Chemical Company as DOWFAX™ 2A1, DOWFAX™ 3B2, DOWFAX™ 8390,DOWFAX™ C6L, DOWFAX™ C10L).

In one implementation, the emulsifier is a cationic surfactant. Somesuitable cationic surfactants which can be used include an ammoniumsalt, especially a primary and a quaternary ammonium salt with straightchain alkyl group, such as a primary ammonium salt or an amino acidcontaining a straight chain alkyl with 3 carbons to 17 carbons,cetyltrimethylammonium bromide (CTAB), cetyltrimethylammonium chloride(CTAC), distearyldimethylammonium chloride, distearyldimethylammoniumbromide, stearylbenzyldimethylammonium chloride, n-alkyltriethylammoniumbromides or chloride, n-alkyltriethylammonium bromides or chloride andso on, wherein the carbon number of the n-alkyl is 13, 15, 17, 21, or23, and Lauryl methyl gluceth-10 hydroxypropyldimonium chloride.

In one implementation, the emulsifier is an amphoteric surfactant.Suitable amphoteric surfactants include N-coco β-amino propionic acid;N-lauryl-, myristyl β-amino propionic acid, disodium N-tallowβ-iminodipropionate; N-coco β-amino butyric acid; and coco betaine inamounts of about 0.5 weight percent to about 5 weight percent,N-coco-3-aminopropionic acid/sodium salt, N-tallow3-imminodipropionatedisodium salt,N-carboxymethyl-N-dimethyl-N-9-octadecenyl ammonium hydroxide, andN-cocoamidethyl-N-hydroxyethylglycine/sodium salt.

The emulsifier component in the resin precursor composition may compriseat least 0.1 wt. %, 1 wt. %, 2 wt. %, 5 wt. %, 10 wt. %, 15 wt. %, or 17wt. % based on the total weight of the resin precursor composition. Theemulsifier component may comprise up to 1 wt. %, 2 wt. %, 5 wt. %, 10wt. %, 15 wt. %, 17 wt. %, or 20 wt. % based on the total weight of theresin precursor composition. The amount of emulsifier component in theresin precursor composition may be from about 0.1 wt. % to about 20 wt.% relative to the total weight of the emulsifier (e.g., from about 1 wt.% to about 5 wt. %; from about 5 wt. % to about 10 wt. %; from about 10wt. % to about 15 wt. %; or from about 15 wt. % to about 20 wt. %).

The resin precursor formulation may further comprise one or morehydrophobes. The hydrophobe may be part of the emulsifier component.Suitable hydrophobes include hexadecane, octadecane, hexadecanol, orpolydimethylsiloxane.

The hydrophobe component in the resin precursor composition may compriseat least 0.1 wt. %, 1 wt. %, 2 wt. %, 5 wt. %, 8 wt. %, or 0 wt. % basedon the total weight of the resin precursor composition. The hydrophobecomponent may comprise up to 1 wt. %, 2 wt. %, 5 wt. %, 8 wt. %, 9 wt.%, or 10 wt. % based on the total weight of the resin precursorcomposition. The amount of hydrophobe component in the resin precursorcomposition may be from about 0.1 wt. % to about 10 wt. % relative tothe total weight of the emulsifier (e.g., from about 1 wt. % to about 5wt. %; from about 5 wt. % to about 10 wt. %).

The resin precursor composition may further comprise one or morephotoinitiator components (5). In the radiation curing process, thephotoinitiator component initiates the curing in response to incidentradiation. The selection of the type of the photoinitiator component inthe resin precursor composition is generally dependent on the wavelengthof curing radiation employed in curing the resin precursor composition.Typically, the peak absorption wavelengths of selected photoinitiatorvary with the range of wavelength of curing radiation to effectivelyutilize radiation energy, especially using ultraviolet light asradiation.

Examples of suitable photoinitiators include, but are not limited to,1-hydroxycyclohexylphenyl ketone, 4-isopropylphenyl-2-hydroxy-2-methylpropan-1-one,1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one,2,2-dimethyl-2-hydroxy-acetophenone, 2,2-dimethoxy-2-phenylacetophenone,2-hydroxy-2-methylpropionphenone, Diphenyl (2,4,6-trimethylbenzoyl)phosphine oxide, bis(2,6-dimethoxy-benzoyl)-2,4,6 trimethyl phenylphosphine oxide,2-methyl-1-1[4-(methylthio)phenyl]-2-morpholino-propan-1-one,3,6-bis(2-methyl-2-morpholino-propionyl)-9-n-octylcarbazole,2-benzyl-2-(dimethylamino)-1-(4-morpholinyl)phenyl)-1-butanone,benzophenone, 2,4,6-trimethylbenzophenone, isopropyl thioxanthone.Suitable blends of photoinitiators commercially available include, butare not limited to, those under the designations of Darocur 4265,Irgacure 1173, Irgacure 2022, Irgacure 2100 from Ciba® SpecialtyChemicals; and Esacure KT37, Esacure KT55, Esacure KT0046 fromLamberti®).

The photoinitiator component in the resin precursor composition maycomprise at least 0.1 wt. %, 1 wt. %, 2 wt. %, 5 wt. %, 10 wt. %, 15 wt.%, or 17 wt. % based on the total weight of the resin precursorcomposition. The photoinitiator component may comprise up to 1 wt. %, 2wt. %, 5 wt. %, 10 wt. %, 15 wt. %, 17 wt. %, or 20 wt. % based on thetotal weight of the resin precursor composition. The amount ofphotoinitiator component in the resin precursor composition may be fromabout 0.1 wt. % to about 20 wt. % relative to the total weight of theresin precursor composition (e.g., from about 1 wt. % to about 5 wt. %;from about 5 wt. % to about 10 wt. %; from about 10 wt. % to about 15wt. %; or from about 15 wt. % to about 20 wt. %).

The resin precursor composition may further comprise reactive diluents(6). Any suitable reactive diluent suitable to achieve the desired padporosity may be used. Exemplary reactive diluents are described herein.

The resin precursor composition may further comprise inorganicparticles, organic particles or both (7). Because the 3D printingprocess involves layer-by-layer sequential deposition of at least onecomposition per layer, it may also be desirable to additionally depositinorganic or organic particles disposed upon or within a pad layer toobtain a certain pad property and/or to perform a certain function. Theinorganic or organic particles may be in the 50 nanometer (nm) to 100micrometer (μm) range in size and may be added to the precursormaterials prior to being dispensed by the 3D printer 306 or added to anuncured printed layer in a ratio of between 1 and 50 weight percent (wt.%). The inorganic or organic particles may be added to during the porouspolishing pad formation process to improve the ultimate tensilestrength, improve yield strength, improve the stability of the storagemodulus over a temperature range, improve heat transfer, adjust asurfaces zeta potential, and adjust a surface's surface energy.

The particle type, chemical composition, or size, and the addedparticles may vary by application or desired effect that is to beachieved. The inorganic or organic particles may be in the 25 nanometer(nm) to 100 micrometer (μm) range in size and may be added to theprecursor materials prior to being dispensed by the droplet ejectingprinter or added to an uncured printed layer in a ratio of between 1 andabout 50 weight percent (wt. %). In some implementations, the particlesmay include intermetallics, ceramics, metals, polymers and/or metaloxides, such as ceria, alumina, silica, zirconia, nitrides, carbides, ora combination thereof. In one example, the inorganic or organicparticles disposed upon or within a pad may include particles of highperformance polymers, such PEEK, PEK, PPS, and other similar materialsto improve the thermal conductivity and/or other mechanical propertiesof the porous polishing pad.

The particle component in the resin precursor composition may compriseat least 0.1 wt. %, 1 wt. %, 2 wt. %, 5 wt. %, 10 wt. %, 15 wt. %, or 17wt. % based on the total weight of the resin precursor composition. Theparticle component may comprise up to 1 wt. %, 2 wt. %, 5 wt. %, 10 wt.%, 15 wt. %, 17 wt. %, or 20 wt. % based on the total weight of theresin precursor composition. The amount of particle component in theresin precursor composition may be from about 0.1 wt. % to about 20 wt.% relative to the total weight of the resin precursor composition (e.g.,from about 1 wt. % to about 5 wt. %; from about 5 wt. % to about 10 wt.%; from about 10 wt. % to about 15 wt. %; or from about 15 wt. % toabout 20 wt. %).

The resin precursor composition may further comprise one or moreadditional components (8). Additional additives include, but are notlimited to stabilizers, surfactants, leveling additives, pH adjusters,sequestering agents, polymer spheres and colorants.

In some implementations, it is desirable to select a surfactant and/orperform a process on the resin precursor composition to assure that thedispersion of one or more components within resin precursor composition,such as the porosity-forming agent and/or particles, is substantiallyuniform. The “process” performed on the resin precursor composition isalso referred to herein as a dispersion process. In one configuration, aprocess is performed on the resin precursor composition that causes thedispersion of the porosity-forming agent within the formed emulsion tobe substantially uniform. In another configuration, a process isperformed on a resin precursor composition that contains a surfactant,with an HLB ranging from 3 to 20, that causes the dispersion of theporosity-forming agent within the formed emulsion to be substantiallyuniform. In some implementations, the dispersed regions of theporosity-forming agent within the formed resin precursor composition isselected such that each dispersed region (e.g., more than one) is only apercentage of the size of the droplet of the resin precursor compositiondispensed during the formation of a layer during the additivemanufacturing process.

The process of dispensing the droplet of the resin precursor compositionis discussed further below. In one example, the droplet of the resinprecursor composition used to form part of a layer of the porouspolishing pad has a physical size that is between about 10 and 200micrometers (μm), such as between about 50 and 150 μm, in diameter, andthe regions of the porosity-forming agent within the mixed resinprecursor composition are between about 1% and 20% of the physicaldroplet size (e.g., 0.5 μm-30 μm in size). In one configuration, thedroplet of the resin precursor composition has a volume between about 10and about 420 picoliters. It is believed that forming a substantiallyuniform mixture of the porosity-forming agent can be useful to assurethat the porosity in the deposited/printed and cured material issubstantially uniform. In some implementations, the dispersion processincludes a method of agitating and/or providing a high shear mixingprocess, for example by use of an impeller or rotor type mixing device,to assure that the dispersion of components within resin precursorcomposition is substantially uniform.

In some implementations, the resin precursor composition includespolymer spheres, such as 100 nm-1 μm of diameter sized polymernano-spheres or micro-spheres that are disposed within the droplets thatare used to form the CMP pads. In some implementations, the polymersphere is between 100 nm and 20 μm in size, such as between 100 nm and 5μm in size. In some additive manufacturing implementations, it may bedesirable to dispense a resin precursor composition containing dropletout of a first nozzle and also dispense a droplet of a polymer spherecontaining formulation out of a second nozzle so that the two dispenseddroplets can mix to form a complete droplet that can then be partiallyor fully cured to form part of the growing polishing pad.

The polymer spheres may comprise one or more solid polymer materialsthat have desirable mechanical properties, thermal properties, wearproperties, degradation properties, or other useful property for usewithin the formed advanced polishing pad. Alternately, the polymerspheres may comprise a solid polymer shell that encloses a liquid (e.g.,water) or gas material so that the polymer sphere will provide desirablemechanical, thermal, wear, or other useful property to the formedadvanced polishing pad. The polymer spheres may include materials thathave hydrophilic and/or have hydro-degradable behaviors, such ashydrogels and poly(lactic-co-glycolic acid), PLGA, which degrade in thepresence of an aqueous solutions. The polymer spheres are typicallyuniformly dispersed in the droplet formulations and in the curedmaterials after performing the additive manufacturing process (e.g., 3Dprinting).

In some configurations, during a CMP polishing process, the polymerspheres are configured to dissolve into the aqueous slurry or degrade inthe presence of slurry, and leave a pore (e.g., 100 nm-1 μm porefeature) in the exposed surface of the advanced polishing pad. It isbelieved that the use of this type of polymer sphere benefits padsurface interaction with slurry and slurry nanoparticle (such as ceriaoxide and silicon dioxide) loading on the pad, which can enhance thepolishing removal rate and reduce the common wafer-to-wafer removal ratedeviations found in CMP processes.

In one implementation, the method of agitating and/or providing a highshear mixing process is performed with an emulsification apparatus.Examples of an emulsification apparatus that is used include, but arenot limited to, an ultrasonic homogenizer, TK Homomixer (manufactured byPRIMIX Corporation), TK Filmics (manufactured by PRIMIX Corporation), ahigh pressure homogenizer (PANDA 2K, manufactured by GEA Niro Soavi),Microfluidizer® (manufactured by Microfluidics), Nanomizer (manufacturedby Yoshida Kikai Co., Ltd.), and the like.

In some implementations, the dispersion process may be performed justprior to placing the resin precursor composition within the hardwareused to deposit the resin precursor composition on a substrate. In oneexample, the resin precursor composition is mixed minutes, or even 1-2hours, before depositing the resin precursor composition using thehardware in the deposition section 355 of an additive manufacturingsystem 350 (FIG. 3A), which is discussed below. In some implementations,the dispersion process may be performed prior to the shipment, ortransfer, of the resin precursor composition from a point where theresin precursor composition is blended (e.g., precursor formulationsection 354 in FIG. 3A) to the point where the resin precursorcomposition is deposited (e.g., deposition section 355). In thisexample, the resin precursor composition is mixed days or weeks beforethe resin precursor composition is deposited/printed by the hardwarefound within the deposition section 355 of an additive manufacturingsystem 350 (FIG. 3A).

In some implementations, it is desirable to deliver components of theresin precursor composition separately during deposition. In oneimplementation, for example, the porosity-forming agent is depositedseparately from the other components of the resin precursor composition.In implementations where the resin precursor is deposited separatelyfrom the porosity-forming agent(s), the resin precursor formulation maycomprise at least one of the following components as describedherein: 1) one or more oligomer components, (2) one or more monomercomponents, (3) one or more emulsifiers/surfactants, (4) aphotoinitiator component, (5) reactive diluents, (6) inorganicparticles, organic particles or both, and (7) additional additives. Theporosity-forming agent may be part of a porosity-forming agent mixturecontaining additional components. For example, the porosity-formingagent may be combined with any of the following components as describedherein: 1) one or more oligomer components, (2) one or more monomercomponents, (3) one or more emulsifiers/surfactants, (4) aphotoinitiator component, (5) reactive diluents, (6) inorganicparticles, organic particles or both, and (7) additional additives.

Additive Manufacturing Apparatus and Process Examples

FIG. 3A is a schematic sectional view of an additive manufacturingsystem 350 that can be used to form a porous polishing pad using anadditive manufacturing process according to one or more implementationsof the present disclosure. An additive manufacturing process mayinclude, but is not limited to a process, such as a polyjet depositionprocess, inkjet printing process, fused deposition modeling process,binder jetting process, powder bed fusion process, selective lasersintering process, stereolithographic process, vat photopolymerizationprocess, digital light processing, sheet lamination process, directedenergy deposition process, or other similar 3D deposition process.

The additive manufacturing system 350 generally includes a precursordelivery section 353, a precursor formulation section 354 and adeposition section 355. The precursor formulation section 354 includes asection of the additive manufacturing system 350 where the resinprecursor components positioned in the precursor delivery section 353are mixed to form one or more resin precursor compositions. Thedeposition section 355 will generally include an additive manufacturingdevice, or hereafter printing station 300, that is used to deposit oneor more resin precursor compositions on layers disposed over a support302. The porous polishing pad 200 may be printed on the support 302within the printing station 300. Typically, the porous polishing pad 200is formed layer-by-layer using one or more droplet ejecting printers306, such as printer 306A and printer 306B illustrated in FIG. 3A, froma CAD (computer-aided design) program. The printers 306A, 306B and thesupport 302 may move relative to each other during the printing process.

The droplet ejecting printer 306 may include one or more print heads 308(e.g., print heads 308A, 308B) having one or more nozzles (e.g., nozzles309-312) for dispensing liquid precursors. In the implementation of FIG.3A, the printer 306A includes print head 308A that has a nozzle 309 anda print head 308B having a nozzle 310. The nozzle 309 may be configuredto dispense a first liquid precursor composition to form a first polymermaterial, such as a porous polymer, while the nozzle 310 may be used todispense a second liquid precursor to form a second polymer material,such as a non-porous polymer, or a porous polymer. The liquid precursorcompositions may be dispensed at selected locations or regions to form aporous polishing pad that has desirable properties. These selectedlocations collectively form the target printing pattern that can bestored as a CAD-compatible file that is then read by an electroniccontroller 305, which controls the delivery of the droplets from thenozzles of the droplet ejecting printer 306.

The electronic controller 305 is generally used to facilitate thecontrol and automation of the components within the additivemanufacturing system 350, including the printing station 300. Theelectronic controller 305 can be, for example, a computer, aprogrammable logic controller, or an embedded controller. The electroniccontroller 305 typically includes a central processing unit (CPU) (notshown), memory (not shown), and support circuits for inputs and outputs(I/O) (not shown). The CPU may be one of any form of computer processorsthat are used in industrial settings for controlling various systemfunctions, substrate movement, chamber processes, and control supporthardware (e.g., sensors, motors, heaters, etc.), and monitor theprocesses performed in the system. The memory is connected to the CPU,and may be one or more of a readily available non-volatile memory, suchas random access memory (RAM), flash memory, read only memory (ROM),floppy disk, hard disk, or any other form of digital storage, local orremote. Software instructions and data can be coded and stored withinthe memory for instructing the CPU. The support circuits are alsoconnected to the CPU for supporting the processor in a conventionalmanner. The support circuits may include cache, power supplies, clockcircuits, input/output circuitry, subsystems, and the like. A program(or computer instructions) readable by the electronic controller 305determines which tasks are performable by the components in the additivemanufacturing system 350. The program may be software readable by theelectronic controller 305 that includes code to perform tasks relatingto monitoring, execution and control of the delivery and positioning ofdroplets delivered from the printer 306, and the movement, support,and/or positioning of the components within the printing station 300along with the various process tasks and various sequences beingperformed in the electronic controller 305.

After 3D printing, the porous polishing pad 200 may be solidified orpartially solidified by use of a curing device 320 that is disposedwithin the deposition section 355 of the additive manufacturing system350. The curing process performed by the curing device 320 may beperformed by heating the printed polishing pad to a curing temperatureor exposing the pad to one or more forms of electromagnetic radiation orelectron beam curing. In one example, the curing process may beperformed by exposing the printed polishing pad to radiation 321generated by an electromagnetic radiation source, such as a visiblelight source, an ultraviolet light source, x-ray source, or other typeof electromagnetic wave source that is disposed within the curing device320.

The additive manufacturing process offers a convenient and highlycontrollable process for producing porous polishing pads with discretefeatures formed from different materials and/or different compositionsof materials.

In another implementation, the first polishing elements 204 and/or thesecond polishing element(s) 206 may each be formed from a mixture of twoor more compositions. In one example, a first composition may bedispensed in the form of droplets by a first print head, such as theprint head 308A, and the second composition may be dispensed in the formof droplets by a second print head, such as the print head 308B of theprinter 306A. To form first polishing elements 204 with a mixture of thedroplets delivered from multiple print heads typically includes thealignment of the pixels corresponding to the first polishing elements204 on predetermined pixels within a deposition map found in theelectronic controller 305. The print head 308A may then align with thepixels corresponding to where the first polishing elements 204 are to beformed and then dispense droplets on the predetermined pixels. Theporous polishing pad may thus be formed from a first composition ofmaterials that is formed by depositing droplets of a first dropletcomposition and a second material that comprises a second composition ofmaterials that is formed by depositing droplets of a second dropletcomposition.

FIG. 3B is a schematic cross-sectional view of a portion of the printingstation 300 and the porous polishing pad 200 during the padmanufacturing process. The printing station 300, as shown in FIG. 3B,includes two printers 306A and 306B that are used to sequentially form aportion of the porous polishing pad 200. The portion of the porouspolishing pad 200 shown in FIG. 3B may, for example, include part ofeither the first polishing element 204 or the second polishing elements206 in the finally formed porous polishing pad 200. During processingthe printers 306A and 306B are configured to deliver droplets “A” or“B,” respectively, to a first surface of the support 302 and thensuccessively to a surface of the growing polishing pad that is disposedon the support 302 in a layer-by-layer process.

As shown in FIG. 3B, a second layer 348 is deposited over a first layer346 which has been formed on the support 302. In one implementation, thesecond layer 348 is formed over the first layer 346, which has beenprocessed by the curing device 320 that is disposed downstream from theprinters 306A and 306B in the pad manufacturing process. In someimplementations, portions of the second layer 348 may be simultaneouslyprocessed by the curing device 320 while one or more of the printers306A and 306B are depositing droplets “A” and/or “B” onto the surface346A of the previously formed first layer 346. In this case, the layerthat is currently being formed may include a processed portion 348A andan unprocessed portion 348B that are disposed on either side of a curingzone 349A. The unprocessed portion 348B generally includes an array ofdispensed droplets, such as dispensed droplets 343 and 347, which aredeposited on the surface 346A of the previously formed first layer 346by use of the printers 306B and 306A, respectively.

FIG. 3C is a close up cross-sectional view of a dispensed droplet 343that is disposed on a surface 346A of the previously formed first layer346. Based on the properties of the materials within the dispenseddroplet 343, and due to surface energy of the surface 346A the dispenseddroplet will spread across the surface an amount that is larger than thesize of the original dispensed droplet (e.g., droplets “A” or “B”), dueto surface tension. The amount of spread of the dispensed droplet willvary as a function of time from the instant that the droplet isdeposited on the surface 346A. However, after a very short period oftime (e.g., <1 second) the spread of the droplet will reach anequilibrium size, and have an equilibrium contact angle α. The spread ofthe dispensed droplet across the surface affects the resolution of theplacement of the droplets on the surface of the growing polishing pad,and thus the resolution of the features and material compositions foundwithin various regions of the final polishing pad.

In some implementations, it is desirable to expose one or both of thedroplets “A” and “B” after they have been contact with the surface ofthe substrate for a period of time to cure, or “fix,” each droplet at adesired size before the droplet has a chance to spread to its uncuredequilibrium size on the surface of the substrate. In this case, theenergy supplied to the dispensed droplet and surface on which thedroplet is placed by the curing device 320 and the droplet's materialcomposition are adjusted to control the resolution of each of thedispensed droplets. Therefore, one optional parameter to control or tuneduring a 3D printing process is the control of the dispensed droplet'ssurface tension relative to the surface on which the droplet isdisposed.

In some implementations, it is desirable to add one or more curingenhancement components (e.g., photoinitiators) to the droplet'sformulation to control the kinetics of the curing process, preventoxygen inhibition, and/or control the contact angle of the droplet onthe surface on which the droplet is deposited. One will note that thecuring enhancement components will generally include materials that areable to adjust: 1) the amount of bulk curing that occurs in the materialin the dispensed droplet during the initial exposure to a desired amountof electromagnetic radiation, 2) the amount of surface curing thatoccurs in the material in the dispensed droplet during the initialexposure to a desired amount of electromagnetic radiation, and 3) theamount of surface property modification (e.g., additives) to the surfacecured region of the dispensed droplet. The amount of surface propertymodification to the surface cured region of the dispensed dropletgenerally includes the adjustment of the surface energy of the cured orpartially cured polymer found at the surface of the dispensed and atleast partially cured droplet.

It has been found that it is desirable to partially cure each dispenseddroplet to “fix” its surface properties and dimensional size during theprinting process. Further, it has also been found the partial curing ofthe droplet allows for the removal of the porosity-forming agent (e.g.,water) after the initial pad structure has been formed. The ability to“fix” the droplet at a desirable size can be accomplished by adding adesired amount of at least one curing enhancement components to thedroplet's material composition and delivering a sufficient amount ofelectromagnetic energy from the curing device 320 during the additivemanufacturing process. In some implementations, it is desirable to use acuring device 320 that is able to deliver between about 1 milli-jouleper centimeter squared (mJ/cm²) and 100 mJ/cm², such as about 10-20mJ/cm², of ultraviolet (UV) light to the droplet during the additivelayer formation process. The UV radiation may be provided by any UVsource, such as mercury microwave arc lamps (e.g., H bulb, H+ bulb, Dbulb, Q bulb, and V bulb type lamps), pulsed xenon flash lamps,high-efficiency UV light emitting diode arrays, and UV lasers. The UVradiation may have a wavelength between about 170 nm and about 500 nm.

In some implementations, the size of dispensed droplets “A”, “B” may befrom about 10 to about 200 microns, such as about 50 to about 70microns. Depending on the surface energy (dynes) of the substrate orpolymer layer that the droplet is dispensed over and upon, the uncureddroplet may spread on and across the surface to a fixed droplet size343A of between about 10 and about 500 microns, such as between about 50and about 200 microns. In one example, the height of such a droplet maybe from about 5 to about 100 microns, depending on such factors assurface energy, wetting, and/or resin precursor composition, which mayinclude other additives, such as flow agents, thickening agents, andsurfactants. One source for the additives is BYK-Gardner GmbH ofGeretsried, Germany.

In some implementations, it is generally desirable to select aphotoinitiator, an amount of the photoinitiator in the dropletcomposition, and the amount of energy supplied by curing device 320 toallow the dispensed droplet to be “fixed” in less than about 1 second,such as less than about 0.5 seconds after the dispensed droplet has comein contact with the surface on which it is to be fixed. The actual timeit takes to partially cure the dispensed droplet, due to the exposure todelivered curing energy, may be longer or shorter than the time that thedroplet resides on the surface before it is exposed to the deliveredradiation, since the curing time of the dispensed droplet will depend onthe amount of radiant energy and wavelength of the energy provide fromthe curing device 320. In one example, an exposure time used topartially cure a 120 micrometer (μm) dispensed droplet is about 0.4microseconds (μs) for a radiant exposure level of about 10-15 mJ/cm² ofUV radiation. In an effort to “fix” the droplet in this short timeframeone should position the dispense nozzle of the droplet ejecting printer306 a short distance from the surface of the surface of the porouspolishing pad, such as between 0.1 and 10 millimeters (mm), or even 0.5and 1 mm, while the surface 346A of the porous polishing pad are exposedto the radiation 321 delivered from the curing device 320.

It has also been found that by controlling droplet composition, theamount of cure of the previously formed layer (e.g., surface energy ofthe previously formed layer), the amount of energy from the curingdevice 320 and the amount of the photoinitiator in the dropletcomposition, the contact angle α of the droplet can be controlled tocontrol the fixed droplet size, and thus the resolution of the printingprocess. In one example, the underlying layer cure may be a cure ofabout 70% acrylate conversion. A droplet that has been fixed, or atleast partially cured, is also referred to herein as a cured droplet. Insome implementations, the fixed droplet size 343A is between about 10and about 200 microns. In some implementations, the contact angle, alsoreferred to herein as the dynamic contact angle (e.g., non-equilibriumcontact angle), for a “fixed” droplet can be desirably controlled to avalue of at least 50°, such as greater than 55°, or even greater than60°, or even greater than 70°.

The resolution of the pixels within a pixel chart that is used to form alayer, or a portion of a layer, by an additive manufacturing process canbe defined by the average “fixed” size of a dispensed droplet. Thematerial composition of a layer, or portion of a layer, can thus bedefined by a “dispensed droplet composition,” which a percentage of thetotal number of pixels within the layer, or portion of the layer, thatinclude droplets of a certain droplet composition. In one example, if aregion of a layer of a formed porous polishing pad is defined as havinga dispensed droplet composition of a first dispensed droplet compositionof 60%, then 60% percent of the pixels within the region will include afixed droplet that includes the first material composition. In caseswhere a portion of a layer contains more than one material composition,it may also be desirable to define the material composition of a regionwithin a porous polishing pad as having a “material composition ratio.”The material composition ratio is a ratio of the number of pixels thathave a first material composition disposed thereon to the number ofpixels that have a second material composition disposed thereon.

In one example, if a region was defined as containing 1,000 pixels,which are disposed across an area of a surface, and 600 of the pixelscontain a fixed droplet of a first droplet composition and 400 of thepixels contain a fixed droplet of a second droplet composition then thematerial composition ratio would include a 3:2 ratio of the firstdroplet composition to the second droplet composition. In configurationswhere each pixel may contain greater than one fixed droplet (e.g., 1.2droplets per pixel) then the material composition ratio would be definedby the ratio of the number of fixed droplets of a first material to thenumber of fixed droplets of a second material that are found within adefined region. In one example, if a region was defined as containing1,000 pixels, and there were 800 fixed droplets of a first dropletcomposition and 400 fixed droplets of a second droplet compositionwithin the region, then the material composition ratio would be 2:1 forthis region of the porous polishing pad.

The amount of curing of the surface of the dispensed droplet that formsthe next underlying layer is a polishing pad formation processparameter, since the amount of curing in this “initial dose” affects thesurface energy that the subsequent layer of dispensed droplets will beexposed to during the additive manufacturing process. The amount of theinitial cure dose is also influential since it will also affect theamount of curing that each deposited layer will finally achieve in theformed polishing pad, due to repetitive exposure of each deposited layerto additional transmitted curing radiation supplied through thesubsequently deposited layers, as they are grown thereon. It isgenerally desirable to prevent over curing of a formed layer, since itwill affect the material properties of the over cured materials and/orthe wettability of the surface of the cured layer to subsequentlydeposited dispensed droplets in subsequent steps.

In one example, to effect polymerization of a 10-30 micron thick layerof dispensed droplets may be performed by dispensing each droplet on asurface and then exposing the dispensed droplet to UV radiation at aradiant exposure level of between about 10 and about 15 mJ/cm² after aperiod of time of between about 0.1 seconds and about 1 second haselapsed. However, in some implementations, the radiation level deliveredduring the initial cure dose may be varied layer-by-layer. For example,due to differing dispensed droplet compositions in different layers, theamount of UV radiation exposure in each initial dose may be adjusted toprovide a desirable level of cure in the currently exposed layer, andalso to one or more of the underlying layers.

In some implementations, it is desirable to control the dropletcomposition and the amount of energy delivered from the curing device320 during the initial curing step, which is a step in which thedeposited layer of dispensed droplets are directly exposed to the energyprovided by the curing device 320, to cause the layer to only partiallycure a desired amount. In general, it is desirable for the initialcuring process to predominantly surface cure the dispensed dropletversus bulk cure the dispensed droplet, since controlling the surfaceenergy of the formed layer is significant for controlling the dispenseddroplet size. In one example, the amount that a dispensed droplet ispartially cured can be defined by the amount of chemical conversion ofthe materials in the dispensed droplet. In one example, the conversionof the acrylates found in a dispensed droplet that is used to form aurethane polyacrylate containing layer, is defined by a percentage x,which is calculated by the equation:

x=1−[(A _(C═C) /A _(C═O))_(x)/(A _(C═C) /A _(C═O))₀],

where A_(C═C) and A_(C═O), are the values of the C═C peak at 910 cm⁻¹and the C═O peaks at 1700 cm⁻¹ found using FT-IR spectroscopy. Duringpolymerization, C═C bonds within acrylates are converted to C—C bond,while C═O within acrylates has no conversion. The intensity of C═C toC═O hence indicates the acrylate conversion rate. The A_(C═C)/A_(C═O)ratio refers to the relative ratio of C═C to C═O bonds within the cureddroplet, and thus the (A_(C═C)/A_(C═O))₀ denotes the initial ratio ofA_(C═C) to A_(C═O) in the droplet, while (A_(C═C)/A_(C═O))_(x) denotesthe ratio of A_(C═C) to A_(C═O) on the surface of the substrate afterthe droplet has been cured.

In some implementations, the amount that a layer is initially cured maybe equal to or greater than about 70% of the dispensed droplet. In someconfigurations, it may be desirable to partially cure the material inthe dispensed droplet during the initial exposure of the dispenseddroplet to the curing energy to a level from about 70% to about 80%, sothat the target contact angle of the dispensed droplet may be attained.It is believed that the uncured or partially acrylate materials on topsurface are copolymerized with the subsequent droplets, and thus yieldcohesion between the layers.

The process of partially curing a dispensed droplet during the initiallayer formation step can also be significant to assure water removalfrom the polishing pad structure to form the pores within the padstructure.

The process of partially curing a dispensed droplet during the initiallayer formation step can also be significant to assure that there willbe some chemical bonding/adhesion between subsequently deposited layers,due to the presence of residual unbonded groups, such as residualacrylic groups. Since the residual unbonded groups have not beenpolymerized, they can be involved in forming chemical bonds with asubsequently deposited layer. The formation of chemical bonds betweenlayers can thus increase the mechanical strength of the formed porouspolishing pad in the direction of the layer-by-layer growth during thepad formation process (e.g., Z-direction in FIG. 3B). As noted above,the bonding between layers may thus be formed by both physical and/orchemical forces.

The mixture of the dispensed droplet, or positioning of the dispenseddroplets, can be adjusted on a layer-by-layer basis to form layers thatindividually have tunable properties, and a porous polishing pad thathas desirable pad properties that are a composite of the formed layers.In one example, as shown in FIG. 3B, a mixture of dispensed dropletsincludes a 50:50 ratio of the dispensed droplets 343 and 347 (or amaterial composition ratio of 1:1), wherein the dispensed droplet 343includes at least one different material from the material found in thedispensed droplet 347.

Properties of portions of the pad body 202, such as the first polishingelements 204 and/or second polishing elements 206 may be adjusted ortuned according to the ratio and/or distribution of a first compositionand a second composition that are formed from the positioning of thedispensed droplets during the deposition process. For example, theweight % of the first composition may be from about 1% by weight basedon total composition weight to about 100% based on total compositionweight. In a similar fashion, the second composition may be from about1% by weight based on total composition weight to about 100% based ontotal composition weight. Depending on the material properties that aredesired, such as hardness and/or storage modulus, compositions of two ormore materials can be mixed in different ratios to achieve a desiredeffect. In one implementation, the composition of the first polishingelements 204 and/or second polishing elements 206 is controlled byselecting at least one composition or a mixture of compositions, andsize, location, and/or density of the droplets dispensed by one or moreprinters. Therefore, the electronic controller 305 is generally adaptedto position the nozzles 309-310, 311-312 to form a layer that hasinterdigitated droplets that have been positioned in a desired densityand pattern on the surface of the porous polishing pad that is beingformed.

In some configurations, dispensed droplets may be deposited in such away as to ensure that each drop is placed in a location where it doesnot blend with other drops, and thus each remains a discrete material“island” prior to being cured. In some configurations, the dispenseddroplets may also be placed on top of prior dispensed droplets withinthe same layer to increase the build rate or blend material properties.Placement of droplets relative to each other on a surface may also beadjusted to allow partial mixing behavior of each of the dispenseddroplets in the layer. In some cases, it may be desirable to place thedroplets closer together or farther apart to provide more or less mixingof the components in the neighboring droplets, respectively. It has beenfound that controlling droplet placement relative to other dispenseddroplets and the composition of each droplet can have an effect on themechanical and polishing properties of the formed porous polishing pad.

Even though only two compositions are generally discussed herein forforming the first polishing elements 204 and/or second polishingelements 206, implementations of the present disclosure encompassforming features on a porous polishing pad with a plurality of materialsthat are interconnected via compositional gradients. In someconfigurations, the composition of the first polishing elements 204and/or second polishing elements 206 in a porous polishing pad areadjusted within a plane parallel to the polishing surface and/or throughthe thickness of the porous polishing pad, as discussed further below.

The ability to form compositional gradients and the ability to tune thechemical content locally, within, and across a porous polishing pad areenabled by “ink jettable” low viscosity compositions, or low viscosity“inks” in the 3D printing arts that are used to form the droplets “A”and/or “B” illustrated in FIG. 3B. The low viscosity inks are“pre-polymer” compositions and are the “precursors” to the formed firstpolishing elements 204 and second polishing elements 206 found in thepad body 202. The low viscosity inks enable the delivery of a widevariety of chemistries and discrete compositions that are not availableby conventional techniques (e.g., molding and casting), and thus enablecontrolled compositional transitions or gradients to be formed withindifferent regions of the pad body 202. This may be achieved by theaddition and mixing of viscosity thinning reactive diluents to highviscosity functional oligomers to achieve the appropriate viscosityformulation, followed by copolymerization of the diluent(s) with thehigher viscosity functional oligomers when exposed to a curing energydelivered by the curing device 320. The reactive diluents may also serveas a solvent, thus eliminating the use of inert non-reactive solvents orthinners that should be removed at each step.

Referring to the precursor delivery section 353 and precursorformulation section 354 of FIG. 3A, in one implementation, a firstporosity-forming agent/emulsifier mixture 352, a first precursor 356,and optionally a second precursor 357 are mixed with a diluent 358 toform a first printable ink composition 359, which is delivered toreservoir 304B of the printer 306B, and used to form portions of the padbody 202. Similarly, a second porosity-forming agent/emulsifier mixture365, a third precursor 366, and optionally a fourth precursor 367 can bemixed with a diluent 368 to form a second printable ink composition 369,which is delivered to reservoir 304A of the printer 306A, and used toform another portion of the pad body 202. In some implementations, thefirst precursor 356 and the third precursor 366 each comprise anoligomer, such as multifunctional oligomer, the second precursor 357 andthe fourth precursor 367 each comprise a multifunctional monomer, thediluent 358 and the diluent 368 each comprise a reactive diluent (e.g.,monomer) and/or initiator (e.g., photo-initiator), and theporosity-forming agent/emulsifier mixtures 352, 365 provide the porousstructure when removed from the pad body.

One example of a first printable ink composition 359 may include a firstprecursor 356 which includes a reactive difunctional oligomer,comprising aliphatic chain segments, which may have a viscosity fromabout 1,000 centipoise (cP) at 25 degrees Celsius, to about 12,000 cP atdegrees Celsius, is then mixed with and thus diluted by a 10 cP atdegrees Celsius reactive diluent (e.g., diluent 358), such asmonoacrylate, to create a new composition that has new viscosity. Theprintable composition thus obtained may exhibit a viscosity from about80 cP to about 110 cP at 25 degrees Celsius, and a viscosity from about15 cP to about 30 cP at 70 degrees Celsius, which may be effectivelydispensed from a 3D printer ink jet nozzle.

Referring to the precursor delivery section 353 and precursorformulation section 354 of FIG. 3A, in one implementation, a firstprecursor 356, and optionally a second precursor 357 are mixed with adiluent 358 to form a first printable ink composition 359, which isdelivered to reservoir 304B of the printer 306B, and used to formportions of the pad body 202. Similarly, the second porosity-formingagent/emulsifier mixture 365, optionally a third precursor 366, andoptionally a fourth precursor (e.g., an emulsifier precursor) 367 can bemixed with a diluent 368 to form a second printable ink composition 369,which is delivered to reservoir 304A of the printer 306A, and removed toform the porous areas of the pad body 202. In some implementations, thefirst precursor 356 and the third precursor 366 each comprise anoligomer, such as a multifunctional oligomer, the second precursor 357and the fourth precursor 367 each comprise a multifunctional monomer,the diluent 358 and the diluent 368 each comprise a reactive diluent(e.g., monomer) and/or initiator (e.g., photo-initiator), and the secondporosity-forming agent/emulsifier mixture 365 is at least one of water,a water-soluble polymer, a water-soluble inert material, awater-containing hydrophilic polymers, a hydrophilic polymerizablemonomers, and combinations thereof. The second printable ink composition369 containing the second porosity-forming agent/emulsifier mixture 365provides the porous structure when removed from the pad body.

One example of a first printable ink composition 359 may include a firstprecursor 356 which includes a reactive difunctional oligomer,comprising aliphatic chain segments, which may have a viscosity fromabout 1,000 centipoise (cP) at 25 degrees Celsius, to about 12,000 cP atdegrees Celsius, is then mixed with and thus diluted by a 10 cP atdegrees Celsius reactive diluent (e.g., diluent 358), such asmonoacrylate, to create a new composition that has new viscosity. Theprintable composition thus obtained may exhibit a viscosity from about80 cP to about 110 cP at 25 degrees Celsius, and a viscosity from about15 cP to about 30 cP at 70 degrees Celsius, which may be effectivelydispensed from a 3D printer ink jet nozzle.

One example of a second printable ink composition 369 may include water.

FIG. 4A is a schematic view of a web based porous polishing pad 400 athat is formed using an additive manufacturing process to form apolishing surface or upper surface(s) 208 that has a gradient inmaterial composition across the polishing surface or upper surface(s)208 (e.g., Y-direction). As shown in FIG. 4A the polishing material maybe disposed over a platen 102 between a first roll 481 and a second roll482. By building a web, or even standard polishing pad, with differingregions of porosity the substrate can be moved over different locationson the web based porous polishing pad 400 a during different portions ofthe polishing process to provide the desired mechanical propertiesduring each phase of the polishing process. One example may involve asubstrate having an initial surface texture removed rapidly using aplanarizing portion of the web based porous polishing pad 400 a that hasa first porosity and then moving the substrate to a second portion ofthe web based porous polishing pad 400 a that has a second porosity thatmay be identical to or different than the first porosity.

FIG. 4B is schematic side cross-sectional view of a porous polishing pad400 b that is formed using an additive manufacturing process to form apolishing base layer 491 that has a gradient in material composition inthe Z-direction. Gradients in the material composition and/or materialproperties of the stacked printed layers of the polishing base layer 491can vary from a high concentration to a low concentration of a firstmaterial to a second material in one direction, or vice versa. In somecases, one or more regions within the porous polishing pad may includemore complex concentration gradients, such as a high/low/high orlow/high/low concentration gradient of at least two materials that havediffering material properties. In one example, at least two materialsthat form the concentration gradient have different porosities. In someconfigurations, the porous polishing pad 400 b may include a polishingelement region 494 that may include discrete regions that include atleast a first polishing element 204 and a second polishing element 206.In one example, the polishing element region 494 may include a portionof a pad body 202 that contains one or more of the structures shown inFIGS. 2A-2E.

In one implementation, the polishing base layer 491 includes ahomogeneous mixture of two or more different materials in each layerformed within the polishing base layer 491. In one example, thehomogeneous mixture may include a mixture of the materials used to formthe first polishing element 204 and the second polishing element 206 ineach layer formed within the polishing base layer 491. In someconfigurations, it is desirable to vary the composition of thehomogeneous mixture of materials layer-by-layer to form a gradient inmaterial composition in the layer growth direction (e.g., Z-direction inFIG. 4B). The phrase homogeneous mixture is intended to generallydescribe a material that has been formed by dispensing and curingprinted droplets that have at least two different compositions withineach layer, and thus may contain a mixture of small regions of the atleast two different compositions that are each sized at a desiredresolution. The interface between the polishing base layer 491 and thepolishing element region 494 may include a homogeneous blend of thematerials found at the upper surface of the polishing base layer 491 andthe lower surface of the polishing element region 494, or include adiscrete transition where the differing material composition in thefirst deposited layer of the polishing element region 494 is directlydeposited on the surface of the polishing base layer 491.

In some implementations of the polishing element region 494, or moregenerally any of the pad bodies 202 described above, it is desirable toform a porosity gradient in the material composition in the firstpolishing elements 204 and/or second polishing elements 206 in adirection normal to the polishing surface of the porous polishing pad.In one example, it is desirable to have higher concentrations of amaterial composition used to form the low porosity features in theprinted layers near the base of the porous polishing pad (e.g., oppositeto the polishing surface), and higher concentrations of a materialcomposition used to form the high porosity features in the printedlayers near the polishing surface of the porous polishing pad. Inanother example, it is desirable to have higher concentrations of amaterial composition used to form the high porosity features in theprinted layers near the base of the porous polishing pad, and a higherconcentration of a material composition used to form the low porosityfeatures in the printed layers near the polishing surface of the porouspolishing pad.

In one implementation, it is desirable to form a gradient in thematerial composition within the material used to form the first and/orsecond polishing elements in a direction normal to the polishing surfaceof the porous polishing pad. In one example, it is desirable to havehigher concentrations of a material composition used to form the secondpolishing elements 206 in the printed layers near the base of the porouspolishing pad (e.g., opposite to the polishing surface), and higherconcentrations of a material composition used to form the firstpolishing elements 204 in the printed layers near the polishing surfaceof the porous polishing pad. In another example, it is desirable to havehigher concentrations of a material composition used to form the firstpolishing elements 204 in the printed layers near the base of the porouspolishing pad, and a higher concentration of a material composition usedto form the second polishing elements 206 in the printed layers near thepolishing surface of the porous polishing pad. For example, a firstlayer may have a material composition ratio of the first printedcomposition to the second printed composition of 1:1, a materialcomposition ratio of the first printed composition to the second printedcomposition of 2:1 in a second layer and a material composition ratio ofthe first printed composition to the second printed composition of 3:1in a third layer. In one example, the first printed composition has ahigher porosity containing material than the second printed composition,and the direction of sequential growth of the first, second and thirdlayers is away from a supporting surface of the porous polishing pad. Agradient can also be formed within different parts of a single layer byadjusting the placement of the printed droplets within the plane of thedeposited layer.

FIG. 5A illustrates a schematic plan view of a pixel chart that is usedto form a region 500 of a layer 522 (FIG. 5B) of a first or a secondpolishing element of a polishing pad that contains pore-forming regionsaccording to one or more implementations of the present disclosure. Inthis example, the pixel chart includes a rectangular pattern ofpore-forming regions 502 that are formed by dispensing one or moredroplets of a porosity-forming agent 504 (FIG. 5B) from a first printhead onto a surface and then at least partially surrounding thepore-forming regions 502 with one or more structural material containingregions 501 that include a material that is formed by dispensingdroplets of one or more resin precursor compositions from at least asecond print head. The porosity-forming agent 504 can then later beremoved in a post processing step or during a polishing process to formpores in one or more layers of the polishing pad. In one example, theporosity-forming agent material is removed from formed advancedpolishing pad when the polishing pad is used in a CMP polishing process.In this example, the porosity-forming agent material may be removed dueto the interaction of the porosity-forming agent disposed at a surface520 of the first or second polishing elements in the advanced polishingpad with one or more components found within a slurry that is disposedbetween the first and/or second polishing elements and a substrate thatis being polished. As shown in FIG. 5A, the pore-forming regions 502 aresurrounded by a structural material containing region 501 that is formedby dispensing droplets of a resin-precursor formulation across a surfaceon which the layer 522 is formed. By use of the various techniquesdescribed herein, compositional gradients in the cured structuralmaterial found within the structural material containing region 501and/or gradients in the size and density of the pore-forming regions 502can be used to form at least part of a complete polishing pad that hasdesirable mechanical and thermal properties. The composition of thepore-forming material disposed within the pore-forming regions 502 anddistribution and size of the pore-forming regions 502 across of theporous polishing pad 200 (i.e., X-Y plane) or through the thickness ofthe polishing element (i.e., Z direction) may vary in any suitablepattern. Although polishing pads described herein are shown to be formedfrom two kinds of materials, this configuration is not intended to belimiting of the scope of the disclosure provided herein, since polishingpads including three or more kinds of materials is within the scope ofthe present disclosure. It should be noted that the compositions of thestructural material found within a polishing pad, such as the polishingpad designs illustrated in FIGS. 2A-2K, may be varied in a similarmanner as discussed above in conjunction with FIGS. 4A-4F. Thus, in someimplementations, the material found within a formed structural materialcontaining region 501 may include a mixture of two or more differentmaterials that varies in one or more directions across (e.g., X and/or Ydirection) or through (e.g., Z direction) the formed layer.

FIG. 5B is a side cross-sectional view of a portion of the region 500illustrated in FIG. 5A according to one or more aspects of the presentdisclosure. The portion shown in FIG. 5B includes a plurality of layers522 that are formed on an optional base layer 521 by use of an additivemanufacturing process as described herein. For clarity of discussionpurposes, the layers are shown in FIG. 5B as being disposed between twodashed lines, however, due to the processes described herein at leastthe structural material containing region 501 parts of adjacent layersmay be formed such that there is no distinct physical division betweenlayers in a formed porous polishing pad 200. The layers 522 each includepore-forming regions 502 that are interspersed between regions of thestructural material containing region 501. As noted above, due to theinteraction of the porosity-forming agent disposed within thepore-forming regions 502 at the surface 520 (i.e., polishing surface112) of the porous polishing pad 200 with a slurry (not shown), which isdisposed within a polishing region 530, the porosity-forming agent 504may be easily removed leaving an unfilled void within the pore-formingregions 502, and thus forming a pore 503.

In one implementation, the pixel charts used to form each layer 522includes pattern that includes an array of porosity-forming agent 504containing pore-forming regions 502 that are formed in a desired patternacross the surface of the formed layer. As noted above, in someimplementations, the pattern of porosity-forming agent 504 containingpore-forming regions 502 can be formed in a rectangular array that has adesirable pitch in both the X and Y directions. However, the pattern ofporosity-forming agent 504 containing pore-forming regions 502 may beformed in any desirable pattern including a hexagonal array ofpore-forming regions 502, a directionally varying pattern ofpore-forming regions 502, a random pattern of pore-forming regions 502or other useful pattern of pore-forming regions 502. In someimplementations, the pixel charts used to form adjacent layers 522 areshifted a desired distance 525 in one or more directions (e.g., X, Y orX and Y directions) relative to each other, or formed in differingrelative X-Y patterns, so that the pore-forming regions 502 are notplaced on top of each other in adjacently positioned layers as thepolishing pad is formed. In one implementation, similarly configuredpatterns of pore-forming regions 502 in adjacent layers may be staggereda desired distance in one or more directions relative to each other sothat the pore-forming regions 502 are not placed on top of each other inthe adjacently positioned layers.

FIG. 5C illustrates is a side cross-sectional view of a portion of theregion 500 illustrated in FIG. 5A according to another aspect of thepresent disclosure. In some implementations, two or more of thedeposited layers may be aligned with each other so that the layers areformed directly on top of each other. In one example, as shown in FIG.5C, two layers 522A and 522B are formed so that the 522A layer isdirectly on top of the layer 522B so that the pore-forming regions 502are placed one on top of the other. The next or subsequent layers maythen be shifted a desired distance 525 relative to the layers 522A-B, sothat the pore-forming regions 502 in the subsequent layers are notplaced on top of the layers 522A-B. This configuration in which two ormore layers, within a larger stack of layers, are formed directly on topof each other may be useful in cases where the fixed droplet sizeresolution in the X and Y directions may be greater than the thicknessof the layer in the Z direction. In one example, the fixed droplet sizein the X and Y directions is twice as large as the thickness in the Zdirection, thus allowing a regular pattern of printed material to beformed in the X, Y and Z directions when two layers are placed on top ofeach other.

Referring back to FIG. 5A, the pixel charts used to form thepore-forming regions 502 and the surrounding structural materialcontaining region 501 within a layer can be used to create portions ofthe polishing features that have a consistent or varying porosity in oneor more directions X, Y, or Z. In one example, the polishing featuresnear an edge region of the advanced polishing pad may include more ofthe resin precursor formulation used to form the structural materialwithin the structural material containing region 501 than theporosity-forming agent 504 containing pore-forming regions 502. Thepolishing features near a center region of the polishing pad may alsoinclude a higher percentage of pore-forming regions 502 per layer (e.g.,higher density) than the polishing features near the edge region. Inthis example, each polishing feature of the same type (e.g., firstpolishing elements 204), or of different types (e.g., first and secondpolishing elements 204, 206), has a unique combination of the resinprecursor formulation, the porosity-forming agent and the density of thepore-forming regions 502 per layer and/or per polishing element. In oneexample, the first polishing elements 204 include a first combination ofthe resin precursor formulation and the porosity-forming agent and thesecond polishing elements 206 include a different second combination ofthe resin precursor formulation and the porosity-forming agent.Therefore, by use of pixel charts, the polishing body can besequentially formed so that a desired porosity gradient is achieved indifferent parts of the polishing body to achieve a desired polishingperformance of the advanced polishing pad.

A method of forming a layer of a porous advanced polishing pad accordingto implementations described herein may include the following steps.First, one or more droplets of a resin composition, such as describedherein, are dispensed in a desired X and Y pattern to form thestructural material portion of a formed layer. In one implementation,the one or more droplets of a resin composition are dispensed on asupport if the one or more droplets constitute a first layer. In someimplementations, the one or more droplets of a resin composition aredispensed on a previously deposited layer (e.g., second layer, etc.).Second, one or more droplets of a porosity-forming compositioncontaining a porosity-forming agent 504 are dispensed in a desired X andY pattern to form the pore-forming regions 502 within the formed layer.In one implementation, the one or more droplets of the porosity-formingcomposition are dispensed on a support if the one or more dropletsconstitute a first layer. In some implementations, the one or moredroplets of the porosity-forming composition are dispensed on apreviously deposited layer. The dispensing processes of the first andsecond operations are typically performed separately in time and atdifferent X-Y coordinates. Next, or third, the dispensed one or moredroplets of the curable resin precursor and the dispensed one or moredroplets of the porosity-forming composition are at least partiallycured. Next, at the optional fourth step, the dispensed one or moredroplets of the curable resin precursor and the dispensed one or moredroplets of the porosity-forming composition are exposed to at least oneof an annealing process, a rinsing process, or both to remove theporosity-forming agent. The rinsing process may include rinsing withwater, another solvent such as alcohol (e.g., isopropanol) or both. Theannealing process may include heating the deposited pad structure to alow temperature (e.g., about 100 degrees Celsius) under a low pressureto vaporize the porosity-forming agent. Next, at the fifth step, anoptional second curing process is performed on the formed layer or finalpad to form the final porous pad structure. In some cases, the first,second, third and fifth processing steps may also be sequentiallyrepeated in any desired order to form a number of stacked layers beforethe fourth step is completed.

In some implementations, the porosity-forming agent 504 may includematerials that have hydrophilic and/or have hydro-degradable behaviors,such as hydrogels, poly(lactic-co-glycolic acid) (PLGA), andPolyethylene glycol (PEG), which degrade in the presence of an aqueoussolutions. In some configurations, during a CMP polishing process, theporosity-forming agent 504 disposed within a formed polishing pad isconfigured to degrade, such as dissolve into an aqueous slurry (e.g.,porosity-forming agent is soluble in the slurry) or break down in thepresence of slurry, and leave a pore (e.g., 100 nm-1 μm opening or void)in the exposed surface of the advanced polishing pad. Theporosity-forming agent 504 may include an oligomeric and/or polymericmaterial that is mixed with an inert soluble component. The inertsoluble components may include ethylene glycol, polyethylene glycol,propylene glycol, diethylene glycol, dipropylene glycol, triethyleneglycol, tetraethylene glycol and glycerol. The inert soluble componentsmay also include corresponding mono alkyl or dialkyl ethers and alkylgroups that may include methyl, ethyl, propyl, isopropyl, butyl orisobutyl groups. In one implementation, the porosity-forming agent 504includes PEG and about 5% to 15% of an oligomeric and/or polymericmaterial, such as an acrylate material. In some configurations, ahydrogel material may be used that is based on polyethylene glycolacrylates or methacrylates. These types of materials can be made frompolar materials that are not soluble in most resin precursorformulations. The hydrogel materials can be made into pore-formingmaterials by cross-linking with diacrylates and dimethacrylates in aratio of about 1 to 10%. The hydrogel materials are formed in this waywill still have solubility in water and can be washed away with water togenerate pores.

In some implementations, the structural material containing region 501may include a material that is formed from one or more of the resinprecursor components disclosed herein. For example, the structuralmaterial containing region 501 may include a material that is formed byuse of a resin precursor component that is selected from, but notrestricted to, at least one of the materials listed in Table 3 orfamilies of materials in which the materials listed in Table 3 are from.Other useful resin precursor components that may be used alone or incombination with one or more of the resin precursor components disclosedherein may also include the thiol-ene and thiol-yne type, epoxy, Michaeladdition type, ring-opening polymerization (ROP), and ring forming orDiels-Alder polymerization (DAP) type components described herein.

In one implementation, the pores formed with the pad body 202 may beformed by causing the porosity-forming agent 504 change phase, such asvaporize, during a subsequent advanced polishing pad formation process.In one example, the porosity within the formed pad may be generated bydelivering electromagnetic radiation to a portion of the polishing padto induce the generation change in phase of the porosity-forming agentmaterial. In one implementation, an advanced polishing pad pre-polymercomposition may contain compounds, polymers, or oligomers that arethermally labile and that may contain of thermally labile groups. Theseporogen and thermally labile groups may be cyclic groups, such asunsaturated cyclic organic groups. The porogen may comprise a cyclichydrocarbon compound. Some exemplary porogens include, but are notrestricted to norbornadiene (BCHD, bicycle(2.2.1)hepta-2,5-diene),alpha-terpinene (ATP), vinylcyclohexane (VCH), phenylacetate, butadiene,isoprene, and cyclohexadiene. In one implementation, a pre-polymer layeris deposited that contains a radiation curable oligomer with acovalently bound porogen group. After exposure to UV radiation and heat,a porous polymer layer may be formed by the effusion of the porogengroup. In another implementation, an advanced polishing pad pre-polymercomposition may contain compounds, polymers, or oligomers that are mixedwith a water containing compound. In this example, a plurality of porouslayers may be formed by sequential layer deposition and then driving outthe water containing compound to form a pore. In other implementations,pores may be generated by thermally induced decomposition of compoundsthat form a gas by-product, such as azo compounds, which decompose toform nitrogen gas.

Alternately, in some implementations, the resin precursor compositionmay include polymer spheres, such as 100 nm-1 μm of diameter sizedpolymer nano-spheres or micro-spheres that are disposed within thedroplets that are used to form the advanced polishing pad. In someimplementations, the polymer sphere is between 100 nm and 20 μm in size,such as between 100 nm and 5 μm in size. In some additive manufacturingimplementations, it may be desirable to dispense a resin precursorcomposition containing droplet out of a first nozzle and also dispense adroplet of a polymer sphere containing formulation out of a secondnozzle so that the two dispensed droplets can mix to form a completedroplet that can then be partially or fully cured to form part of thegrowing polishing pad. In some configurations, during a CMP polishingprocess, the polymer spheres are configured to degrade, such as dissolveinto the aqueous slurry or break down in the presence of slurry, andleave a pore (e.g., 100 nm-1 μm pore feature) in the exposed surface ofthe advanced polishing pad.

The polymer spheres may comprise one or more solid polymer materialsthat have desirable mechanical properties, thermal properties, wearproperties, degradation properties, or other useful property for usewithin the formed advanced polishing pad. Alternately, the polymerspheres may comprise a solid polymer shell that encloses a liquid (e.g.,water) or gas material so that the polymer sphere will provide desirablemechanical, thermal, wear, or other useful property to the formedadvanced polishing pad. The polymer spheres may also be used to formpores within regions of a fixed droplet that is used to form one or moreregions within portions of a formed polishing element (e.g., polishingelements 204 and/or 206) to provide desirable mechanical, thermal, wear,or other useful property to these portions of a formed advancedpolishing pad. The polymer spheres may include materials that havehydrophilic and/or have hydro-degradable behaviors, such as hydrogelsand poly(lactic-co-glycolic acid), PLGA, which degrade in the presenceof an aqueous solutions. The polymer spheres are typically uniformlydispersed in the droplet formulations and in the cured materials afterperforming the additive manufacturing process (e.g., 3D printing).

In some configurations, hydrogel particles may be used that are based onpolyethylene glycol acrylates or methacrylates. These types of particlesare made from polar materials and are not soluble in most formulations.The hydrogel particles can be made into particle form by cross-linkingwith diacrylates and dimethacrylates in a ratio of about 1 to 15%. Thehydrogel particles formed in this way will still have solubility inwater and can be washed away with water to generate pores.

Advance Polishing Pad Formation Process Example

In some implementations, as discussed above, the construction of theporous polishing pad 200 by an additive manufacturing process begins bycreating a CAD model of the porous polishing pad design. This can bedone using existing CAD design software, such as Unigraphics or othersimilar software. An output file, which is generated by the modellingsoftware, is then loaded to an analysis program to ensure that theporous polishing pad design meets the design requirements (e.g., watertight, mass density). The output file is then rendered, and the 3D modelis then “sliced” into a series of 2D data bitmaps, or pixel charts. Asnoted above, the 2D bitmaps, or pixel charts, are used to define thelocations across an X and Y plane where the layers in the porouspolishing pad will be built. In one implementation, the 2D bitmaps ofthe polishing article are represented in a data structure readable by acomputer rendering device or a computer display device.

The computer-readable medium may contain a data structure thatrepresents the polishing article. The data structure may be a computerfile, and may contain information about the structures, materials,textures, physical properties, or other characteristics of one or morearticles. The data structure may also contain code, such as computerexecutable code or device control code that engages selectedfunctionality of a computer rendering device or a computer displaydevice. The data structure may be stored on the computer-readablemedium. The computer-readable medium may include a physical storagemedium such as a magnetic memory, floppy disk, or any convenientphysical storage medium. The physical storage medium may be readable bythe computer system to render the article represented by the datastructure on a computer screen or a physical rendering device, which maybe an additive manufacturing device, such as a 3D printer. In someadditive manufacturing process applications the pixel chart locationswill define where a laser will pulse, and in other applications thelocation where a nozzle will eject a droplet of a material.

The coordinates found in the pixel charts are used to define thelocation at which a specific droplet of uncured polymer will be placedusing, for example, a poly jet print head. Every coordinate for an X andY location and a given pad supporting Z stage position will be definedbased on the pixel charts. Each X, Y and Z location will include eithera droplet dispense or droplet non-dispense condition. Print heads may beassembled in an array in the X and/or Y directions to increase buildrate or to deposit additional types of materials. In the examples shownin FIGS. 2F-2K, the black pixels indicate locations where nozzles willnot deposit materials and the white pixels indicate where nozzles willdeposit materials. By combining the material maps, or pixel charts, ineach formed layer a porous polishing pad of any desirable shape orstructural configuration can be printed by the positioning of thediscrete droplets near one another.

An additive manufacturing device, such as a 3D printer can be used toform a porous polishing pad by depositing water,emulsifiers/surfactants, thermoplastic polymers, depositing and curingof a photosensitive resin precursor compositions, and/or laser pulsetype sintering and fusing of a dispensed powder layer. In someimplementations, the porous polishing pad formation process may includea method of polyjet printing of UV sensitive materials. In thisconfiguration, droplets of a precursor formulation (e.g., firstprintable ink composition 359) are ejected from a nozzle in the dropletejecting printer 306 and resin precursor composition is deposited ontothe build stage. As material is deposited from an array of nozzles, thematerial may be leveled with the use of a roller or other means tosmooth drops into a flat film layer or transfer away excess material.While the droplet is being dispensed, and/or shortly thereafter, a UVlamp or LED radiation source passes over the deposited layer to cure orpartially cure the dispensed droplets into a solid polymer network.

In some implementations, a monochromatic light source (e.g., LED lightsource) is used that has a narrow emitted wavelength range and/or anarrow spot size that is specifically tailored to substantially orpartially cure one or more dispensed droplets, and thus not adverselyaffect other surrounding regions or prior formed layers of the formedadvanced polishing pad. In some implementations, the monochromatic lightsource is configured to deliver wavelengths of light within a rangebetween 100 nm and 500 nm, such as between about 170 nm and 400 nm. Inone example, a UV LED source is configured to deliver UV light within aband of +/−10 nm at a central wavelength of 240 nm, 254 nm, 365 nm, 385nm, 395 nm or 405 nm wavelengths. This process is built layer on top oflayer with adequate cohesion within the layer and between layers toensure the final implementation of the pad model is mechanically sound.

In order to better control the polymer stress through the build process,heat may be added during the formation of one or more of the layers. Thedelivery of heat allows the polymer network formed in each cured orpartially cured layer to relax and thus reduce stress and remove stresshistory in the film. Stress in the film can result in unwanteddeformation of the porous polishing pad during or after the porouspolishing pad formation process. Heating the partially formed polishingpad while it is on the printer's build tray ensures that the final padproperties are set through the layer-by-layer process and a predictablepad composition and polishing result can be achieved. In addition toinducing heat into the porous polishing pad formation process, the areasurrounding the growing polishing pad may be modified to reduce theoxygen exposure to the uncured resin. This can be done by employingvacuum or by flooding the build chamber with nitrogen (N₂) or otherinert gas. The reduction in oxygen over the growing pad will reduce theinhibition of the free radical polymerization reaction, and ensures amore complete surface cure of the dispensed droplets.

Following production of the polishing pad, the polishing pad can beannealed by heating to a temperature above the glass transitiontemperature T_(g) for a period of time to remove water from the formedpad to from the porous pad structure. Optionally, water removal can befacilitated faster under vacuum.

The polishing pad can be further processed using any suitable technique.For example, the polishing pad can be skived or milled to provide apolishing surface. The produced polishing surface can be furtherprocessed using techniques such as conditioning the polishing surface,for example, by diamond conditioning.

Porous Polishing Pad Formulation Examples

As noted above, in some implementations, one or more of the materialsthat are used to form at least one of the two or more polishingelements, such as the first and second polishing elements 204 and 206,is formed by sequentially depositing and post deposition processing ofat least one curable resin precursor composition. In general, thecurable resin precursor compositions, which are mixed during theprecursor formulation process performed in the precursor deliverysection 353 of the additive manufacturing system 350, will include theformulation of resin precursor compositions that contain functionaloligomers, porosity-forming agents (e.g., water), emulsifiers,hydrophobes, reactive diluents and curing components, such asinitiators. Examples of some of these components are listed in Table 1.

TABLE 1 Reference Tg UTS Name Material Information Functionality (° C.)(psi) % Elongation O1 Aliphatic urethane 2 27 5378 79 acrylate oligomerO2 Aliphatic hexafunctional 6 145 11,000 1 urethane acrylate O3 Lowviscosity diacrylate 2 26 1,600 10 oligomer O4 Aliphatic hexafunctional6 120 acrylate O5 Multifunctional urethane 3.4 46 3045 2 acrylateoligomer O6 Aliphatic urethane 2 N/A N/A N/A diacrylate oligomer 1 O7Aliphatic urethane N/A N/A N/A N/A acrylate oligomer 2 O8 Aliphaticpolyester 2 + 2 N/A N/A N/A urethane diacrylate blend with aliphaticdiacrylate O9 Acrylic oligomer N/A N/A N/A N/A M1 Dipropylene glycol 2104 2938 5 diacrylate M2 2-Propenoic acid, 2- 1 5 19 236 phenoxyethylester M3 Tertio-butyl 1 41 cyclohexanol acrylate (TBCHA) M4Polyether-modified polydimethylsiloxane M5 CTFA 2 Ethers 1 32 — — M6EOEO-EA 1 −54 — — M7 2- 1 −3 (((butylamino)carbonyl)oxy)ethyl ester M8Tetrahydrofurfuryl 1 −12 M9 Tetrafunctional 4 N/A N/A N/A polyetheracrylate M10 Isobornyl acrylate 1 N/A N/A N/A P1 2-Hydroxy-2-methyl-1-N/A N/A N/A phenyl-propan-1-one P2 4-Phenylbenzophenone N/A N/A N/A P3Acyl phosphine oxide N/A N/A N/A N/A P4 Bis-benzoyl phosphine N/A N/AN/A N/A oxide P5 Blend of P1 and P3 N/A N/A N/A N/A A1 Acrylated amine<1 N/A N/A N/A synergist A2 Polyoxyethylene alkyl phenyl ether ammoniumsulfate non-migratory surfactant H1 Hexadecane H2 Hexadecanol E1 MAXEMUL6106 E2 E-Sperse RS1618 X1 Diethylene glycol X2 Glycerol X3 Glycerolpropoxylate

Examples of functional oligomers can be found in items O1-O9 in Table 1.Examples of functional reactive diluents and other additives can befound in items M1-M10 in Table 1. Examples of curing components arefound in items P1-P5 and A1 in Table 1. Examples of emulsifiers arefound in items E1-E2 in Table 1. Examples of hydrophobes are found initems H1-H2 in Table 1. Examples of porosity-forming agents are found initems X1-X3 in Table 1. Items O1-O3, M1-M3 and M5-M6 found in Table 1are available from Sartomer USA, item O4 is available from MiwonSpecialty Chemicals Corporation Ltd. of Korea, item O5 is available fromAllnex Corporation of Alpharetta, Ga., USA, item M4 is available fromBYK-Gardner GmbH of Germany and items P1-P5 and A1 are available fromChiba Specialty Chemicals Inc. and RAHN USA Corporation. Item A2 isavailable from Montello, Inc. of Tulsa, Okla. Items H1-H2 in Table 1 areavailable from Sigma-Aldrich® Co. Item E1 is available from CrodaInternational Plc. Item E2 is available from Ethox Chemicals, LLC. ItemsX1-X3 in Table 1 are available from Sigma-Aldrich® Co.

One advantage of the additive manufacturing processes described hereinincludes the ability to form an advance polishing pad that hasproperties and porosity that can be adjusted based on the composition ofthe resin precursor components and structural configuration of thevarious formed materials used within the pad body structure. Theinformation below provides some examples of some material formulationsand the affect that varying various components in these formulationsand/or processing techniques have on some of the properties needed toform a porous polishing pad that will achieve improved polishing resultsover conventional polishing pad designs. The information provided inthese examples can be used to form at least a portion of the porouspolishing pad 200, such as part of the first polishing element 204, thesecond polishing element 206, or both the first and second polishingelements 204 and 206. The examples provided herein are not intended tobe limiting as to the scope of the disclosure provided herein, sinceother similar chemical formulations and processing techniques can beused to adjust some of the properties described herein.

Examples of the curable resin precursor composition components, whichare described above and below, are intended to be comparative examplesand one skilled in the art can find other suitable monomers/oligomersfrom various sources to achieve the desired properties. Some examplesfor reactive diluents are 2-ethylhexyl acrylate, octyldecyl acrylate,cyclic trimethylolpropane formal acrylate, caprolactone acrylate,isobornyl acrylate (IBOA), and alkoxylated lauryl methacrylate. Thefirst material is available from Sigma-Aldrich, and the balance may beobtained from Sartomer USA and/or Rahn AG USA (SR series 203, 217, 238,242, 306, 339, 355, 368, 420, 484, 502, 506A, 508, SR 531, 550, 585,495B, 256, 257, 285, 611, 506, 833S, and 9003B, CD series 421A, 535,545, 553, 590, 730, and 9075, Genomer series 1116, 1117, 1119, 1121,1122, 5142, 5161, 5275, 6058, 7151, and 7210, Genocure series, BP, PBZ,PMP, DETX, ITX, LBC, LBP, TPO, and TPO-L, and Miramer series, M120,M130, M140, M164, M166, and M170). Some examples for difunctionalcross-linkers are bisphenol A glycerolate dimethacrylate, ethyleneglycol dimethacrylate, diethylene glycol dimethacrylate, tetraethyleneglycol dimethacrylate, 1,6-hexanediol diacrylate and 1,4-butanedioldiacrylate, which may be obtained from Sigma-Aldrich. Some examples ofoligomers could include aliphatic oligomers (CN series 131, 131B, 132,152, 508, 549, 2910, 3100 and 3105 from Sartomer USA), polyesteracrylate oligomers (CN series 292, 293, 294E, 299, 704, 2200, 2203,2207, 2261, 2261LV, 2262, 2264, 2267, 2270, 2271E, 2273, 2279, 2282,2283, 2285 and 2303 from Sartomer USA) and aliphatic urethane oligomers(CN series 929, 959, 961H81, 962, 969, 964A85, 965, 968, 980, 986, 989,991, 992, 996, 2921, 9001, 9007, 9013, 9178 and 9783 from Sartomer USA).The agents or additives could be supplied from BYK, such as 3550, 3560,307, 378, 1791, 1794, 9077, A515, A535, JET9510, JET9511, P9908, UV3500,UV3535, DISPERBYK168, and DISPERBYK2008. The first type photoinitiatorcould be from BASF, such as Irgacure series 184, 2022, 2100, 250, 270,295, 369, 379, 500, 651, TPO, TPO-L, 754, 784, 819, 907, 1173, or 4265.Additionally, other functional oligomers and resin precursor compositioncomponents can be purchased from Allnex Corp., such as the Ebecrylseries (EB): 40, 53, 80, 81, 83, 110, 114, 130, 140, 150, 152, 154, 168,170, 180, 220, 230, 242, 246, 264, 265, 270, 271, 284, 303, 350, 411,436, 438, 450, 452, 524, 571, 600, 605, 608, 657, 745, 809, 810, 811,812, 830, 860, 870, 871, 885, 888, 889, 893, 1258, 1290, 1291, 1300,1360, 1710, 3200, 3201, 3411, 3415, 3418, 3500, 3600, 3700, 3701, 3720,4265, 4827, 4833, 4849, 4858, 4883, 5129, 7100, 8100, 8296, 8301, 8311,8402, 8405, 8411, 8412, 8413, 8414, 8465, 8501, 8602, 8701, 8702, 8804,8807, 8808, and 8810. Free and non-migratory (polymerizable) surfactantssuch as triethanol amine (TEA) and Hitenol and Maxemul branded materialsare available from Sigma-Aldrich, Montello, Inc., of Tulsa, Okla. USAand Croda, Inc., of New Castle, Del., USA.

Examples of formulations that contain different porosity are illustratedbelow in Table 2. Example 1 was a control performed without the additionof water and emulsifier. Example 2 was performed with the addition ofwater only. Example 3 was performed with both water and emulsifier.Items 4-7 each represent a formulation that may be modified with water,emulsifiers, or both.

TABLE 2 Average Pore Material Composition Formulation Pore Size SizeItem (See Table 1 Composition (wt. Range (mi- No. Ref. Name) %)(microns) crons) 1 O1:O3:O4:M1 30:33:15:33 2 O1:O3:O4:M1:H₂O30:33:15:33:11 6-130 3 O1:O3:O4:M1:H₂O:E2 30:33:15:33:11:1.1 6-40  15 4O1:M3 45:55 n/a n/a 5 O1:M1 45:55 n/a n/a 6 O1:M3:M1:M2 45:22:22:11 n/an/a 7 O4:O1:M3:M1:M2 30:15:22:22:11 n/a n/a

Example 1 (Control)

As noted in Item 1 in Table 2, a formulation that containsmultifunctional oligomers with 01:03:04:M1 was mixed in the ratio of30:33:15:33. Then photoinitiators and additives (P1:P2:A1 in the ratioof 67:8.25:24.75) in about 3% by weight of the formulation were addedfor curing. This mixture (8 g) was placed in an aluminum cup and exposedto UV radiation to cure the acrylate monomers. This did not result inmeasureable pores.

Example 2

Referring to Item 2 in Table 2, Example 1 was repeated by adding water(11 wt. %; 1.6 g) and photoinitiator (6.4 g) and was shaken very well.The mixture was cured similar to the Example 1. Then water was removedby heating to 60 degrees Celsius for 2 days under vacuum. The SEM imagerevealed the pore size as 6-130 microns and it is illustrated in FIG.6A.

Example 3

Referring to Item 3 in Table 2, Example 2 was repeated by addingemulsifier E2 (1.1 wt. %) and shaken very well. It was then sonicatedusing Kaijo's Sono Cleaner Model 100Z for 3 minutes. This mixture wastransferred to aluminum cup and exposed to UV radiation to cure theacrylate monomers similar to Example 2. Then water was removed similarto Example 1. The SEM image revealed the pore size as 6-40 microns andis illustrated in FIG. 6B. The pore size depicted in the SEM image ofFIG. 6B is considerably reduced compared to the pore size depicted inthe SEM image of FIG. 6A with an average size of 15 microns having anarrower pore size distribution. In some cases, a narrower pore sizedistribution is desirable to control the spread of variation inmechanical properties of the formed porous material within desiredregions of the porous polishing pad, provide more consistent andreproducible pad polishing properties, and control the slurry retentionprovided by the porous structure(s).

Table 3 depicts various formulations that may be used to form the porouspad structures described herein. Item No. 8 does not contain aporosity-forming agent. Item 9, Item 10 and Item 11 contain 20 wt. %, 30wt. %, and 40 wt. % of a porosity-forming agent X1 respectively.

TABLE 3 Material Composition Formulation Viscosity CA with Item (SeeTable 1 Ref. Composition (wt. at 70° C. CA with water (°) No. Name) %)(cps) water (°) after 5 min 8 O1:O2:O3:M1:M3:M4: 24.1:12.1:0.20:24.7:P2:P4:A1:A2 26.5:0.10:0.20: 1.61:0.60:9.97 9 O1:O2:O3:M1:M3:M4:19.3:9.64:0.16:19.7: 12.0 57 47 P2:P4:A1:A2:X1 21.2:0.08:0.16:1.29:0.48:7.98: 20.0 10 O1:O2:O3:M1:M3:M4: 16.9:8.44:0.14:17.3: 7.3 8377 P2:P4:A1:A2:X1 18.6:0.07:0.14: 1.13:0.42:6.98: 30.0 11O1:O2:O3:M1:M3:M4: 14.5:7.23:0.12:14.8: 6.5 88 76 P2:P4:A1:A2:X115.9:0.06:0.12: 0.97:0.36:5.98: 40.0

Table 4 depicts various formulations that may be used to form the porouspad structures described herein.

TABLE 4 Material Viscosity Composition Formulation CA drop Viscosity at70° C. (See Table 1 Composition (wt. on cured at 70° C. (cps) after ItemNo. Ref. Name) %) film (°) (cps) 90 C./3 days 12 Item 8:X1 90:10 34 12.512.9 13 Item 90:10:0.2:0.1 39 12.3 12.5 8:X1:O3:M4 14 Item80:10:10:0.2:0.1 43 17.3 20.3 8:X1:A2:O3:M4

Table 5 depicts various hypothetical formulations that may be used toform the porous pad structures described herein.

TABLE 5 Component Weight % range Formulation of Item 8 60 to 90 Diethylene glycol 0 to 40 Glycerol 0 to 40 Glycerol propoxylate 0 to 30CN132 0 to 2  BYK307 0 to 2  Hitenol BC-10 0 to 15 Maxemul 6106 0 to 15

FIG. 7 is a schematic perspective sectional view of a porous polishingpad 700 according to one implementation of the present disclosure. Theporous polishing pad 700 includes a second polishing element 702 that isa soft or low storage modulus E′ material similar to the secondpolishing elements 206 of the 3D printed polishing pad. Similar to thesecond polishing elements 206, the second polishing element 702 may beformed from one or more elastomeric polymer compositions that mayinclude polyurethane and aliphatic segments. The porous polishing pad700 includes a plurality of surface features 706 extending from thesecond polishing element 702. Outer surfaces 708 of the surface features706 may be formed from a porous material. In one implementation, theouter surface 708 of the surface features 706 may be formed from thesame material or the same composition of materials as the secondpolishing element 702. The surface features 706 may also include a hardfeature 704 embedded therein. The high storage modulus E′ or hardfeatures 704 may be formed from a material or a composition of materialsthat is harder than the surface features 706. The high storage modulusE′ or hard features 704 may be formed from materials similar to thematerial or materials of the hard or high storage modulus E′ features ofthe porous polishing pad 200, including crosslinked polymer compositionsand compositions containing aromatic groups. The embedded hard features704 alter the effective hardness of the surface features 706, and thusprovide a desired target pad hardness for polishing. The soft or lowstorage modulus E′ polymeric layer of the outer surface 708 can be usedto reduce defects and improve planarization on the substrate beingpolished. Alternatively, a soft or low storage modulus E′ polymermaterial may be printed on surfaces of other polishing pads of thepresent disclosure to provide the same benefit.

FIG. 8 is a schematic perspective sectional view of a porous polishingpad 800 having one or more observation windows 810. The porous polishingpad 800 may have a pad body 802. The pad body 802 may include one ormore features such as a plurality of first polishing elements 804extending from second polishing elements 806 for polishing. The secondpolishing elements 806 and the first polishing elements 804 may beformed from materials similar to those for the second polishingelement(s) 206 and first polishing elements 204 of the porous polishingpad 200. The first polishing elements 804 may be arranged in anysuitable patterns according to the present disclosure.

The one or more observation windows 810 may be formed from a transparentmaterial or compositions to allow observation of the substrate beingpolished. The one or more observation windows 810 may be formed through,and/or about portions of, the second polishing elements 806 or the firstpolishing elements 804. In some implementations, the one or moreobservation windows 810 may be formed from a material that issubstantially transparent, and thus is able to transmit light emittedfrom a laser and/or white light source for use in a CMP optical endpointdetection system. The optical clarity should be high enough to provideat least about 25% (e.g., at least about 50%, at least about 80%, atleast about 90%, at least about 95%) light transmission over thewavelength range of the light beam used by the end point detectionsystem's optical detector. Typical optical end point detectionwavelength ranges include the visible spectrum (e.g., from about 400 nmto about 800 nm), the ultraviolet (UV) spectrum (e.g., from about 300 nmto about 400 nm), and/or the infrared spectrum (e.g., from about 800 nmto about 1550 nm). In one implementation, the one or more observationwindows 810 is formed from a material that has a transmittance of >35%at wavelengths between 280-800 nm. In one implementation, the one ormore observation windows 810 is formed from a material that has atransmittance of >35% at wavelengths between 280-399 nm, and atransmittance of >70% at wavelengths between 400-800 nm. In someimplementations, the one or more observation windows 810 is formed froma material that has a low refractive index that is about the same asthat of the polishing slurry and has a high optical clarity to reducereflections from the air/window/water interface and improve transmissionof the light through the one or more observation windows 810 to and fromthe substrate.

In one implementation, the one or more observation windows 810 may beformed from a transparent printed material, includingpolymethylmethacrylate (PMMA). In another implementation, the window isformed using transparent polymeric compositions that contain epoxidegroups, wherein the compositions may be cured using a cationic cure, andmay provide additional clarity and less shrinkage. In a similarimplementation, the window may be formed from a mixture of compositionsthat undergo both cationic and free radical cure. In anotherimplementation, the window may be produced by another process, and maybe mechanically inserted into a preformed opening in the porouspolishing pad that is formed by a 3D process.

FIG. 9 is a schematic perspective sectional view of a porous polishingpad 900 including a backing layer 906. The porous polishing pad 900includes a second polishing element 904 and a plurality of firstpolishing elements 902 protruding from the second polishing element 904.The porous polishing pad 900 may be similar to any of the porouspolishing pads 200, 700, 800 described above, with the exception thatthe backing layer 906 is attached to the second polishing element 904.The backing layer 906 may provide a desired compressibility to theporous polishing pad 900. The backing layer 906 may also be used toalter the overall mechanical properties of the porous polishing pad 900to achieve a desired hardness and/or have desired storage modulus E′ andloss modulus E″. The backing layer 906 may have a hardness value of lessthan 70 Shore A scale. In one implementation, the backing layer 906 maybe formed from an open-cell or a closed-cell foam, such as polyurethaneor polysiloxane (silicone), so that under pressure the cells collapseand the backing layer 906 compresses. In another implementation, thebacking layer 906 may be formed from natural rubber, EPDM rubber(ethylene propylene diene monomer), nitrile, or neoprene(polychloroprene).

Although polishing pads described herein are circular in shape,polishing particles according to the present disclosure may include anysuitable shape, such as polishing webs configured to move linearlyduring polishing.

The increased complexity of polishing pad designs that will be needed topolish the next generation IC devices greatly increases themanufacturing complexity of these polishing pads. There are non-additivemanufacturing type processes and/or subtractive process that may beemployed to manufacture some aspects of these complex pad designs. Theseprocesses may include multi-material injection molding and/or sequentialstep UV casting to form material layers from single discrete materials.These forming steps are then typically followed by machining and postprocessing using milling, grinding or laser ablation operations or othersubtractive techniques.

FIGS. 10A-10O depict SEM images of various implementations of porouspads formed according to implementations described herein. FIGS. 10A-10Cdepict SEM images for a porous pad formed using a 5×5 bitmap design.FIG. 10C depicts the formed porous pad containing the porosity-formingagent after deposition. FIG. 10B depicts the formed porous pad afterexposure to a washing/rinsing process to remove the porosity-formingagent. FIG. 10A depicts the formed porous pad after exposure to both awashing/rinsing process and an anneal process to remove theporosity-forming agent.

FIGS. 10D-10F depict SEM images for a porous pad formed using a 4×4bitmap design. FIG. 10F depicts the formed porous pad containing theporosity-forming agent after deposition. FIG. 10E depicts the formedporous pad after exposure to a washing/rinsing process to remove theporosity-forming agent. FIG. 10D depicts the formed porous pad afterexposure to both a washing/rinsing process and an anneal process toremove the porosity-forming agent.

FIGS. 10G-101 depict SEM images for a porous pad formed using a 3×3bitmap design. FIG. 10I depicts the formed porous pad containing theporosity-forming agent after deposition. FIG. 10H depicts the formedporous pad after exposure to a washing/rinsing process to remove theporosity-forming agent. FIG. 10G depicts the formed porous pad afterexposure to both a washing/rinsing process and an anneal process toremove the porosity-forming agent.

FIGS. 10J-10L depict SEM images for a porous pad formed using a 2×2bitmap design. FIG. 10L depicts the formed porous pad containing theporosity-forming agent after deposition. FIG. 10K depicts the formedporous pad after exposure to a washing/rinsing process to remove theporosity-forming agent. FIG. 10J depicts the formed porous pad afterexposure to both a washing/rinsing process and an anneal process toremove the porosity-forming agent.

FIGS. 10M-10O depict SEM images for a porous pad formed using a 1×1bitmap design. FIG. 10O depicts the formed porous pad containing theporosity-forming agent after deposition. FIG. 10N depicts the formedporous pad after exposure to a washing/rinsing process to remove theporosity-forming agent. FIG. 10M depicts the formed porous pad afterexposure to both a washing/rinsing process and an anneal process toremove the porosity-forming agent.

FIG. 11A-11B depict SEM images of surfaces of porous pads formedaccording to implementations described herein.

FIG. 12 depict SEM images of surfaces of porous pads formed according toimplementations described herein. In some implementations, as shown inFIG. 12, the majority of the pores form adjacent to the interfacebetween the deposited layers.

FIG. 13 is a flow chart depicting a method 1300 of forming a porous padaccording to implementations described herein. At operation 1310, one ormore droplets of a resin composition are dispensed. In oneimplementation, the one or more droplets of a resin composition aredispensed on a support if the one or more droplets constitute a firstlayer. In some implementations, the one or more droplets of a resincomposition are dispensed on a previously deposited layer. At operation1320, one or more droplets of a porosity-forming composition containinga porosity-forming agent are dispensed. In one implementation, the oneor more droplets of the porosity-forming composition are dispensed onthe support if the one or more droplets constitute a first layer. Insome implementations, the one or more droplets of the porosity-formingcomposition are dispensed on a previously deposited layer. Thedispensing processes of operation 1310 and operation 1320 are typicallyperformed separately. Optionally, at operation 1330, the dispensed oneor more droplets of the curable resin precursor and the dispensed one ormore droplets of the porosity-forming composition are partially cured.Operations 1310, 1320, and 1330 may be repeated to form a 3-D relief. Atoperation 1340, the dispensed one or more droplets of the curable resinprecursor and the dispensed one or more droplets of the porosity-formingcomposition are exposed to at least one of an annealing process, arinsing process, or both to remove the porosity-forming agent. Therinsing process may include rinsing with water, another solvent such asalcohol (e.g., isopropanol) or both. The annealing process may includeheating the deposited pad structure to a low temperature (e.g., about100 degrees Celsius) under a low pressure to vaporize theporosity-forming agent. At operation 1350, an optional curing process isperformed to form the final porous pad structure.

While the foregoing is directed to implementations of the presentdisclosure, other and further implementations of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

1. A resin precursor composition, comprising: a first precursorformulation, comprising: a first resin precursor component thatcomprises a multifunctional acrylate oligomer; a second resin precursorcomponent that comprises a multifunctional acrylate monomer; asurfactant; and a porosity-forming agent selected from glycols, water,water-soluble inert materials, water-containing hydrophilic polymers,hydrophilic polymerizable monomers, and combinations thereof, whereinthe first precursor formulation has a first viscosity that enables thefirst precursor formulation to be dispensed to form a portion of apolishing article by an additive manufacturing process.
 2. The resinprecursor composition of claim 1, further comprising a first curingagent that comprises a photoinitiator.
 3. The resin precursorcomposition of claim 2, wherein the photoinitiator is selected frombenzoin ethers, benzyl ketals, acetyl phenones, alkyl phenones phosphineoxides, benzophenone compounds, thioxanthone compounds, or combinationsthereof.
 4. The resin precursor composition claim 1, wherein thesurfactant is a non-ionic surfactant having an HLB value ranging from 4to about
 14. 5. The resin precursor composition of claim 1, wherein thesurfactant is selected from anionic surfactants, non-ionic surfactants,cationic surfactants, amphoteric surfactants, or combinations thereof.6. The resin precursor composition of claim 1, wherein the surfactant isa low HLB surfactant having an HLB of 10 or less.
 7. The resin precursorcomposition of claim 1, wherein the surfactant has a low HLB value in arange of 3 to 6 and is selected from sorbitan monostearate, sorbitandistearate, sorbitan tristearate, polyglycerol oleates, lecithin,sorbitan monooleate, glycerol monooleate, or combinations thereof. 8.The resin precursor composition of claim 1, wherein the surfactant has alow HLB value and is selected from lanolin, lanolin alcohols, orcombinations thereof.
 9. The resin precursor composition of claim 1,wherein water is present between 5 wt. % to about 30 wt. % of the firstresin precursor formulation.
 10. The resin precursor composition ofclaim 1, wherein the first resin precursor component comprises analiphatic multifunctional urethane acrylate that has a functionalitythat is greater than or equal to
 2. 11. The resin precursor compositionof claim 10, wherein the second resin precursor component comprises2-ethylhexyl acrylate, octyldecyl acrylate, cyclic trimethylolpropaneformal acrylate, caprolactone acrylate, alkoxylated lauryl methacrylate,or combinations thereof.
 12. The resin precursor composition of claim 1,wherein the first viscosity is from about 15 cP to about 30 cP at 70degrees Celsius.
 13. The resin precursor composition of claim 1, whereinthe multifunctional acrylate oligomer is an aliphatic multifunctionalurethane acrylate oligomer, and the second resin precursor componentfurther comprises a multifunctional acrylate monomer.
 14. The resinprecursor composition of claim 1, wherein the first resin precursorcomponent forms a material that has a glass transition temperature thatis greater than 40 degrees Celsius, and an amount of the first resinprecursor component is greater than an amount of the second resinprecursor component in the first precursor formulation.
 15. The resinprecursor composition of claim 1, wherein the surfactant is an ionicsurfactant selected from tetrabutylammonium tetrabutyl,tetrafluoroborate, hexafluorophosphate, tetrabutylammonium benzoate, orcombinations thereof.
 16. The resin precursor composition of claim 15,further comprising glycol.
 17. A porous polishing pad formed using theresin precursor composition of claim
 1. 18. The porous polishing pad ofclaim 17, wherein the porous polishing pad has a void volume fraction ofabout 1% to about 20%.
 19. The porous polishing pad of claim 17,comprising: a composite polishing pad body, having: a first groovedsurface; and a second flat surface opposite the first grooved surface.20. A method of forming a porous polishing pad, comprising: depositing aplurality of composite layers with a 3D printer to reach a targetthickness, wherein depositing the plurality of composite layerscomprises: dispensing one or more droplets of a curable resin precursorcomposition onto a support; and dispensing one or more droplets of aporosity-forming composition onto the support, wherein at least onecomponent of the porosity-forming composition is removable to form thepores in the porous polishing pad.